diff --git a/src/core/access.py b/src/core/access.py
index 871fb48f..920e920a 100644
--- a/src/core/access.py
+++ b/src/core/access.py
@@ -1,13 +1,13 @@
 from typing import TYPE_CHECKING, Any
 
 from database.users import User
-from schemas.datasets.openml import Visibility
+from schemas.datasets import Visibility
 
 if TYPE_CHECKING:
     from sqlalchemy.engine import Row
 
 
-async def _user_has_access(
+async def user_has_access(
     dataset: Row[Any],
     user: User | None = None,
 ) -> bool:
diff --git a/src/core/conversions.py b/src/core/conversions.py
index 5ac13c4a..597b76a4 100644
--- a/src/core/conversions.py
+++ b/src/core/conversions.py
@@ -3,7 +3,7 @@
 from typing import Any
 
 
-def _str_to_num(string: str) -> int | float | str:
+def str_to_num(string: str) -> int | float | str:
     """Try to convert the string to integer, otherwise float, otherwise returns the input."""
     if string.isdigit():
         return int(string)
@@ -23,7 +23,7 @@ def nested_str_to_num(obj: Any) -> Any:
     For dictionaries, only the values will be converted.
     """
     if isinstance(obj, str):
-        return _str_to_num(obj)
+        return str_to_num(obj)
     if isinstance(obj, Mapping):
         return {key: nested_str_to_num(val) for key, val in obj.items()}
     if isinstance(obj, Iterable):
diff --git a/src/core/formatting.py b/src/core/formatting.py
index a4b09e8a..33146f4a 100644
--- a/src/core/formatting.py
+++ b/src/core/formatting.py
@@ -1,11 +1,7 @@
-import html
+"""Utilities for formatting and converting text data."""
 
-from config import get_config
-from database.schema.base import UntypedRow
-from schemas.datasets.openml import DatasetFileFormat
 
-
-def _str_to_bool(string: str) -> bool:
+def str_to_bool(string: str) -> bool:
     if string.casefold() in ["true", "1", "yes", "y"]:
         return True
     if string.casefold() in ["false", "0", "no", "n"]:
@@ -14,30 +10,7 @@ def _str_to_bool(string: str) -> bool:
     raise ValueError(msg)
 
 
-def _format_parquet_url(dataset: UntypedRow) -> str | None:
-    if dataset.format.lower() != DatasetFileFormat.ARFF:
-        return None
-
-    minio_base_url = get_config().routing.minio_url
-    ten_thousands_prefix = f"{dataset.did // 10_000:04d}"
-    padded_id = f"{dataset.did:04d}"
-    return f"{minio_base_url}datasets/{ten_thousands_prefix}/{padded_id}/dataset_{dataset.did}.pq"
-
-
-def _format_dataset_url(dataset: UntypedRow) -> str:
-    base_url = get_config().routing.server_url
-    filename = f"{html.escape(dataset.name)}.{dataset.format.lower()}"
-    return f"{base_url}data/v1/download/{dataset.file_id}/{filename}"
-
-
-def _safe_unquote(text: str | None) -> str | None:
-    """Remove any open and closing quotes and return the remainder if non-empty."""
-    if not text:
-        return None
-    return text.strip("'\"") or None
-
-
-def _csv_as_list(text: str | None, *, unquote_items: bool = True) -> list[str]:
+def csv_as_list(text: str | None, *, unquote_items: bool = True) -> list[str]:
     """Return comma-separated values in `text` as list, optionally remove quotes."""
     if not text:
         return []
diff --git a/src/routers/types.py b/src/core/types.py
similarity index 92%
rename from src/routers/types.py
rename to src/core/types.py
index fe945778..6d33ec95 100644
--- a/src/routers/types.py
+++ b/src/core/types.py
@@ -1,3 +1,5 @@
+"""Common types used in the definition of schemas and models."""
+
 from typing import Annotated
 
 from pydantic import Field
diff --git a/src/database/datasets.py b/src/database/datasets.py
index 5cb99d03..1d6bf05d 100644
--- a/src/database/datasets.py
+++ b/src/database/datasets.py
@@ -7,15 +7,15 @@
 from sqlalchemy import text
 from sqlalchemy.exc import IntegrityError
 
+from core.types import Identifier, TagString
 from database.exceptions import (
     _DUPLICATE_ENTRY,
     _FOREIGN_KEY_CONSTRAINT_FAILED,
     DuplicatePrimaryKeyError,
     ForeignKeyConstraintError,
 )
-from database.schema.base import UntypedRow
-from routers.types import Identifier, TagString
-from schemas.datasets.openml import DatasetStatus, Feature
+from database.models.base import UntypedRow
+from schemas.datasets import DatasetStatus, Feature
 
 if TYPE_CHECKING:
     from sqlalchemy.ext.asyncio import AsyncConnection
diff --git a/src/database/setup.py b/src/database/engine.py
similarity index 88%
rename from src/database/setup.py
rename to src/database/engine.py
index cfd23069..80cf0c14 100644
--- a/src/database/setup.py
+++ b/src/database/engine.py
@@ -1,3 +1,5 @@
+"""Functions relating to the database engines."""
+
 import functools
 
 from loguru import logger
@@ -27,11 +29,13 @@ def _create_engine(db_config: DatabaseConfiguration) -> AsyncEngine:
 
 @functools.cache
 def user_database() -> AsyncEngine:
+    """Get a database engine connected to the `openml` database."""
     return _create_engine(get_config().openml_database)
 
 
 @functools.cache
 def expdb_database() -> AsyncEngine:
+    """Get a database engine connected to the `openml_expdb` database."""
     return _create_engine(get_config().expdb_database)
 
 
diff --git a/src/database/evaluations.py b/src/database/evaluations.py
index 14bec4d9..ce0d230a 100644
--- a/src/database/evaluations.py
+++ b/src/database/evaluations.py
@@ -3,9 +3,9 @@
 
 from sqlalchemy import text
 
-from core.formatting import _str_to_bool
-from database.schema.base import UntypedRow
-from schemas.datasets.openml import EstimationProcedure
+from core.formatting import str_to_bool
+from database.models.base import UntypedRow
+from schemas.tasks import EstimationProcedure
 
 if TYPE_CHECKING:
     from sqlalchemy.ext.asyncio import AsyncConnection
@@ -41,7 +41,7 @@ async def get_estimation_procedures(connection: AsyncConnection) -> list[Estimat
     rows = row.mappings().all()
     typed_rows = [
         {
-            k: v if k != "stratified_sampling" or v is None else _str_to_bool(v)
+            k: v if k != "stratified_sampling" or v is None else str_to_bool(v)
             for k, v in row.items()
         }
         for row in rows
diff --git a/src/database/flows.py b/src/database/flows.py
index 830a386b..d245d66d 100644
--- a/src/database/flows.py
+++ b/src/database/flows.py
@@ -3,8 +3,8 @@
 
 from sqlalchemy import text
 
-from database.schema.base import UntypedRow
-from routers.types import Identifier
+from core.types import Identifier
+from database.models.base import UntypedRow
 
 if TYPE_CHECKING:
     from sqlalchemy.ext.asyncio import AsyncConnection
diff --git a/src/database/schema/__init__.py b/src/database/models/__init__.py
similarity index 100%
rename from src/database/schema/__init__.py
rename to src/database/models/__init__.py
diff --git a/src/database/schema/base.py b/src/database/models/base.py
similarity index 96%
rename from src/database/schema/base.py
rename to src/database/models/base.py
index 0a750559..9ded3e22 100644
--- a/src/database/schema/base.py
+++ b/src/database/models/base.py
@@ -18,7 +18,7 @@ class ClassName(ExpDBReflected, Base):
 from sqlalchemy.ext.declarative import DeferredReflection
 from sqlalchemy.orm import DeclarativeBase
 
-from database.setup import expdb_database, user_database
+from database.engine import expdb_database, user_database
 
 UntypedRow = Row[Any]
 
diff --git a/src/database/schema/setups.py b/src/database/models/setups.py
similarity index 81%
rename from src/database/schema/setups.py
rename to src/database/models/setups.py
index 36f96694..3ff94d2f 100644
--- a/src/database/schema/setups.py
+++ b/src/database/models/setups.py
@@ -2,8 +2,8 @@
 
 from sqlalchemy.orm import Mapped, mapped_column
 
-from database.schema.base import Base, ExpDBReflected
-from routers.types import Identifier
+from core.types import Identifier
+from database.models.base import Base, ExpDBReflected
 
 
 class Setup(ExpDBReflected, Base):
diff --git a/src/database/schema/tags.py b/src/database/models/tags.py
similarity index 91%
rename from src/database/schema/tags.py
rename to src/database/models/tags.py
index 5fd687e0..560b6802 100644
--- a/src/database/schema/tags.py
+++ b/src/database/models/tags.py
@@ -5,8 +5,8 @@
 from sqlalchemy import FetchedValue
 from sqlalchemy.orm import Mapped, mapped_column
 
-from database.schema.base import Base, ExpDBReflected
-from routers.types import Identifier, TagString
+from core.types import Identifier, TagString
+from database.models.base import Base, ExpDBReflected
 
 
 class Tag:
diff --git a/src/database/qualities.py b/src/database/qualities.py
index 4899f028..bb239eb3 100644
--- a/src/database/qualities.py
+++ b/src/database/qualities.py
@@ -4,8 +4,8 @@
 
 from sqlalchemy import text
 
-from routers.types import Identifier
-from schemas.datasets.openml import Quality
+from core.types import Identifier
+from schemas.datasets import Quality
 
 if TYPE_CHECKING:
     from sqlalchemy.ext.asyncio import AsyncConnection
diff --git a/src/database/runs.py b/src/database/runs.py
index 0c5c93c2..2a4d5470 100644
--- a/src/database/runs.py
+++ b/src/database/runs.py
@@ -5,8 +5,8 @@
 
 from sqlalchemy import bindparam, text
 
-from database.schema.base import UntypedRow
-from routers.types import Identifier
+from core.types import Identifier
+from database.models.base import UntypedRow
 
 if TYPE_CHECKING:
     from sqlalchemy.ext.asyncio import AsyncConnection
diff --git a/src/database/setups.py b/src/database/setups.py
index 2bd20f86..2808cd98 100644
--- a/src/database/setups.py
+++ b/src/database/setups.py
@@ -6,15 +6,15 @@
 from sqlalchemy import select, text
 from sqlalchemy.exc import IntegrityError
 
+from core.types import Identifier, TagString
 from database.exceptions import (
     _DUPLICATE_ENTRY,
     _FOREIGN_KEY_CONSTRAINT_FAILED,
     DuplicatePrimaryKeyError,
     ForeignKeyConstraintError,
 )
-from database.schema.setups import Setup
-from database.schema.tags import SetupTag
-from routers.types import Identifier, TagString
+from database.models.setups import Setup
+from database.models.tags import SetupTag
 
 if TYPE_CHECKING:
     from sqlalchemy.engine import RowMapping
diff --git a/src/database/studies.py b/src/database/studies.py
index b4a69364..b9617164 100644
--- a/src/database/studies.py
+++ b/src/database/studies.py
@@ -5,9 +5,9 @@
 
 from sqlalchemy import text
 
-from database.schema.base import UntypedRow
+from core.types import Identifier
+from database.models.base import UntypedRow
 from database.users import User
-from routers.types import Identifier
 from schemas.study import CreateStudy, StudyType
 
 if TYPE_CHECKING:
diff --git a/src/database/tasks.py b/src/database/tasks.py
index ae8aaa0e..74c330bb 100644
--- a/src/database/tasks.py
+++ b/src/database/tasks.py
@@ -4,15 +4,15 @@
 from sqlalchemy import select, text
 from sqlalchemy.exc import IntegrityError
 
+from core.types import Identifier, TagString
 from database.exceptions import (
     _DUPLICATE_ENTRY,
     _FOREIGN_KEY_CONSTRAINT_FAILED,
     DuplicatePrimaryKeyError,
     ForeignKeyConstraintError,
 )
-from database.schema.base import UntypedRow
-from database.schema.tags import TaskTag
-from routers.types import Identifier, TagString
+from database.models.base import UntypedRow
+from database.models.tags import TaskTag
 
 if TYPE_CHECKING:
     from sqlalchemy.ext.asyncio import AsyncConnection, AsyncSession
diff --git a/src/database/users.py b/src/database/users.py
index 745e3113..3e46ab08 100644
--- a/src/database/users.py
+++ b/src/database/users.py
@@ -8,7 +8,7 @@
 from sqlalchemy import text
 
 from config import get_config
-from routers.types import Identifier
+from core.types import Identifier
 
 if TYPE_CHECKING:
     from sqlalchemy.ext.asyncio import AsyncConnection
diff --git a/src/main.py b/src/main.py
index 6207b15d..59e1cb8f 100644
--- a/src/main.py
+++ b/src/main.py
@@ -26,19 +26,19 @@
     request_response_logger,
     setup_log_sinks,
 )
-from database.schema.base import reflect_db_schemas
-from database.setup import close_databases
-from routers.openml.datasets import router as datasets_router
-from routers.openml.estimation_procedure import router as estimationprocedure_router
-from routers.openml.evaluations import router as evaluationmeasures_router
-from routers.openml.flows import router as flows_router
-from routers.openml.qualities import router as qualities_router
-from routers.openml.runs import router as run_router
-from routers.openml.setups import router as setup_router
-from routers.openml.study import router as study_router
-from routers.openml.tasks import router as task_router
-from routers.openml.tasktype import router as ttype_router
-from routers.openml.users import router as users_router
+from database.engine import close_databases
+from database.models.base import reflect_db_schemas
+from routers.datasets import router as datasets_router
+from routers.estimation_procedure import router as estimationprocedure_router
+from routers.evaluations import router as evaluationmeasures_router
+from routers.flows import router as flows_router
+from routers.qualities import router as qualities_router
+from routers.runs import router as run_router
+from routers.setups import router as setup_router
+from routers.study import router as study_router
+from routers.tasks import router as task_router
+from routers.tasktype import router as ttype_router
+from routers.users import router as users_router
 
 
 @asynccontextmanager
diff --git a/src/routers/__init__.py b/src/routers/__init__.py
index 21016d13..5d924fcf 100644
--- a/src/routers/__init__.py
+++ b/src/routers/__init__.py
@@ -1 +1 @@
-"""API routers for the OpenML server API."""
+"""Routers for the OpenML API."""
diff --git a/src/routers/openml/datasets.py b/src/routers/datasets.py
similarity index 87%
rename from src/routers/openml/datasets.py
rename to src/routers/datasets.py
index 72c94de3..2718e7b0 100644
--- a/src/routers/openml/datasets.py
+++ b/src/routers/datasets.py
@@ -1,9 +1,18 @@
+"""Defines endpoints relating to Datasets.
+
+A dataset includes both the "data", e.g., the table or parquet file, as well as its metadata.
+The metadata is partially provided by the user (for example, the name or description),
+'features' that are partially parsed from the data file (for example, column names),
+and 'qualities' (or meta-features) that describe the data (for example, number of rows or columns).
+"""
+
 import asyncio
+import html
 import re
 from datetime import datetime
 from enum import StrEnum
 from http import HTTPStatus
-from typing import TYPE_CHECKING, Annotated, Any, Literal, NamedTuple, NotRequired, TypedDict
+from typing import TYPE_CHECKING, Annotated, Any, Literal, NamedTuple
 
 from fastapi import APIRouter, Body, Depends, Query
 from loguru import logger
@@ -11,7 +20,8 @@
 
 import database.datasets
 import database.qualities
-from core.access import _user_has_access
+from config import get_config
+from core.access import user_has_access
 from core.errors import (
     DatasetAdminOnlyError,
     DatasetNoAccessError,
@@ -28,12 +38,16 @@
     TagNotFoundError,
     TagNotOwnedError,
 )
-from core.formatting import (
-    _csv_as_list,
-    _format_dataset_url,
-    _format_parquet_url,
+from core.formatting import csv_as_list
+from core.types import (
+    CasualString128,
+    Identifier,
+    IntegerRange,
+    TagString,
+    integer_range_regex,
 )
 from database.exceptions import DuplicatePrimaryKeyError, ForeignKeyConstraintError
+from database.models.base import UntypedRow
 from database.users import User
 from routers.dependencies import (
     Pagination,
@@ -42,14 +56,8 @@
     fetch_user_or_raise,
     userdb_connection,
 )
-from routers.types import (
-    CasualString128,
-    Identifier,
-    IntegerRange,
-    TagString,
-    integer_range_regex,
-)
-from schemas.datasets.openml import DatasetMetadata, DatasetStatus, Feature, FeatureType
+from schemas.core import TagInfo
+from schemas.datasets import DatasetFileFormat, DatasetMetadata, DatasetStatus, Feature, FeatureType
 
 if TYPE_CHECKING:
     from sqlalchemy.engine import Row
@@ -58,6 +66,22 @@
 router = APIRouter(prefix="/datasets", tags=["datasets"])
 
 
+def _format_parquet_url(dataset: UntypedRow) -> str | None:
+    if dataset.format.lower() != DatasetFileFormat.ARFF:
+        return None
+
+    minio_base_url = get_config().routing.minio_url
+    ten_thousands_prefix = f"{dataset.did // 10_000:04d}"
+    padded_id = f"{dataset.did:04d}"
+    return f"{minio_base_url}datasets/{ten_thousands_prefix}/{padded_id}/dataset_{dataset.did}.pq"
+
+
+def _format_dataset_url(dataset: UntypedRow) -> str:
+    base_url = get_config().routing.server_url
+    filename = f"{html.escape(dataset.name)}.{dataset.format.lower()}"
+    return f"{base_url}data/v1/download/{dataset.file_id}/{filename}"
+
+
 @router.post(
     path="/tag",
 )
@@ -67,6 +91,7 @@ async def tag_dataset(
     user: Annotated[User, Depends(fetch_user_or_raise)],
     expdb_db: Annotated[AsyncConnection, Depends(expdb_connection)],
 ) -> dict[str, dict[str, Any]]:
+    """Add a tag to the dataset, this tag is publicly visible to all users."""
     try:
         await database.datasets.tag(data_id, tag, user_id=user.user_id, connection=expdb_db)
     except ForeignKeyConstraintError:
@@ -85,11 +110,6 @@ async def tag_dataset(
     }
 
 
-class TagInfo(TypedDict):
-    id: str
-    tag: NotRequired[TagString | list[TagString]]
-
-
 @router.post(path="/untag", deprecated=True)
 async def untag_dataset_like_php(
     data_id: Annotated[Identifier, Body()],
@@ -97,6 +117,7 @@ async def untag_dataset_like_php(
     user: Annotated[User, Depends(fetch_user_or_raise)],
     expdb_db: Annotated[AsyncConnection, Depends(expdb_connection)],
 ) -> dict[Literal["data_untag"], TagInfo]:
+    """Remove a tag from the dataset with a response similar to the old PHP server."""
     await untag_dataset(data_id, tag, user, expdb_db)
     tags = await database.datasets.get_tags_for(id_=data_id, connection=expdb_db)
     tag_info: TagInfo = {"id": str(data_id)}
@@ -114,6 +135,7 @@ async def untag_dataset(
     user: Annotated[User, Depends(fetch_user_or_raise)],
     expdb_db: Annotated[AsyncConnection, Depends(expdb_connection)],
 ) -> None:
+    """Remove a tag that you added to a dataset, or from a dataset you uploaded."""
     dataset_tag = await database.datasets.get_tag(identifier, tag, expdb_db)
     if not dataset_tag:
         try:
@@ -130,6 +152,8 @@ async def untag_dataset(
 
 
 class DatasetStatusFilter(StrEnum):
+    """Legal filter values for the Dataset Status filter."""
+
     ACTIVE = DatasetStatus.ACTIVE
     DEACTIVATED = DatasetStatus.DEACTIVATED
     IN_PREPARATION = DatasetStatus.IN_PREPARATION
@@ -182,6 +206,7 @@ async def list_datasets(  # noqa: PLR0913, C901
     status: Annotated[DatasetStatusFilter, Body()] = DatasetStatusFilter.ACTIVE,
     user: Annotated[User | None, Depends(fetch_user)] = None,
 ) -> list[dict[str, Any]]:
+    """List all datasets that match the filters."""
     status_subquery = text(
         """
         SELECT ds1.`did`, ds1.`status`
@@ -308,6 +333,8 @@ async def list_datasets(  # noqa: PLR0913, C901
 
 
 class ProcessingInformation(NamedTuple):
+    """Metadata about an attempt to process a dataset."""
+
     date: datetime | None
     warning: str | None
     error: str | None
@@ -345,7 +372,7 @@ async def _get_dataset_raise_otherwise(
         msg = f"No dataset with id {dataset_id} found."
         raise DatasetNotFoundError(msg)
 
-    if not await _user_has_access(dataset=dataset, user=user):
+    if not await user_has_access(dataset=dataset, user=user):
         msg = f"No access granted to dataset {dataset_id}."
         raise DatasetNoAccessError(msg)
 
@@ -358,6 +385,7 @@ async def get_dataset_features(
     expdb: Annotated[AsyncConnection, Depends(expdb_connection)],
     user: Annotated[User | None, Depends(fetch_user)] = None,
 ) -> list[Feature]:
+    """Return metadata for each feature (column) in the dataset."""
     assert expdb is not None  # noqa: S101
     await _get_dataset_raise_otherwise(dataset_id, user, expdb)
     features, ontologies = await asyncio.gather(
@@ -402,6 +430,7 @@ async def update_dataset_status(
     user: Annotated[User, Depends(fetch_user_or_raise)],
     expdb: Annotated[AsyncConnection, Depends(expdb_connection)],
 ) -> dict[str, str | int]:
+    """Update the status of the dataset. Can be used to deactivate a dataset."""
     dataset = await _get_dataset_raise_otherwise(dataset_id, user, expdb)
 
     can_deactivate = dataset.uploader == user.user_id or await user.is_admin()
@@ -456,8 +485,7 @@ async def get_dataset(
     expdb_db: Annotated[AsyncConnection, Depends(expdb_connection)],
     user: Annotated[User | None, Depends(fetch_user)] = None,
 ) -> DatasetMetadata:
-    assert user_db is not None  # noqa: S101
-    assert expdb_db is not None  # noqa: S101
+    """Get the user-provided metadata for a dataset."""
     dataset = await _get_dataset_raise_otherwise(dataset_id, user, expdb_db)
     if not (
         dataset_file := await database.datasets.get_file(
@@ -482,12 +510,12 @@ async def get_dataset(
     dataset_url = _format_dataset_url(dataset)
     parquet_url = _format_parquet_url(dataset)
 
-    contributors = _csv_as_list(dataset.contributor, unquote_items=True)
-    creators = _csv_as_list(dataset.creator, unquote_items=True)
-    ignore_attribute = _csv_as_list(dataset.ignore_attribute, unquote_items=True)
-    row_id_attribute = _csv_as_list(dataset.row_id_attribute, unquote_items=True)
-    original_data_url = _csv_as_list(dataset.original_data_url, unquote_items=True)
-    default_target_attribute = _csv_as_list(dataset.default_target_attribute, unquote_items=True)
+    contributors = csv_as_list(dataset.contributor, unquote_items=True)
+    creators = csv_as_list(dataset.creator, unquote_items=True)
+    ignore_attribute = csv_as_list(dataset.ignore_attribute, unquote_items=True)
+    row_id_attribute = csv_as_list(dataset.row_id_attribute, unquote_items=True)
+    original_data_url = csv_as_list(dataset.original_data_url, unquote_items=True)
+    default_target_attribute = csv_as_list(dataset.default_target_attribute, unquote_items=True)
 
     return DatasetMetadata(
         id=dataset.did,
diff --git a/src/routers/dependencies.py b/src/routers/dependencies.py
index 87ea5381..f0706ef0 100644
--- a/src/routers/dependencies.py
+++ b/src/routers/dependencies.py
@@ -1,3 +1,8 @@
+"""Common dependencies for router endpoints.
+
+See also https://fastapi.tiangolo.com/reference/dependencies/
+"""
+
 from collections.abc import AsyncGenerator, AsyncIterator
 from typing import TYPE_CHECKING, Annotated
 
@@ -7,7 +12,7 @@
 from sqlalchemy.ext.asyncio import AsyncSession
 
 from core.errors import AuthenticationFailedError, AuthenticationRequiredError
-from database.setup import expdb_database, user_database
+from database.engine import expdb_database, user_database
 from database.users import APIKey, User
 
 if TYPE_CHECKING:
diff --git a/src/routers/openml/estimation_procedure.py b/src/routers/estimation_procedure.py
similarity index 68%
rename from src/routers/openml/estimation_procedure.py
rename to src/routers/estimation_procedure.py
index d8532dcb..d7e76d2f 100644
--- a/src/routers/openml/estimation_procedure.py
+++ b/src/routers/estimation_procedure.py
@@ -1,10 +1,12 @@
+"""Defines endpoints relating to Estimation Procedures."""
+
 from typing import TYPE_CHECKING, Annotated
 
 from fastapi import APIRouter, Depends
 
 import database.evaluations
 from routers.dependencies import expdb_connection
-from schemas.datasets.openml import EstimationProcedure
+from schemas.tasks import EstimationProcedure
 
 if TYPE_CHECKING:
     from sqlalchemy.ext.asyncio import AsyncConnection
@@ -16,5 +18,9 @@
 async def get_estimation_procedures(
     expdb: Annotated[AsyncConnection, Depends(expdb_connection)],
 ) -> list[EstimationProcedure]:
+    """Return a list with descriptions of estimation procedures.
+
+    Estimation procedures define how to evaluate a model, e.g., 5-repeated 2-fold cross-validation.
+    """
     procedures = await database.evaluations.get_estimation_procedures(expdb)
     return list(procedures)
diff --git a/src/routers/openml/evaluations.py b/src/routers/evaluations.py
similarity index 57%
rename from src/routers/openml/evaluations.py
rename to src/routers/evaluations.py
index f2891312..65cb4506 100644
--- a/src/routers/openml/evaluations.py
+++ b/src/routers/evaluations.py
@@ -1,3 +1,5 @@
+"""Defines endpoints relating to Evaluation Measures."""
+
 from typing import TYPE_CHECKING, Annotated
 
 from fastapi import APIRouter, Depends
@@ -15,6 +17,14 @@
 async def get_evaluation_measures(
     expdb: Annotated[AsyncConnection, Depends(expdb_connection)],
 ) -> list[str]:
+    """Return a list of evaluation measure names.
+
+    Evaluation measures are any function that is computed over either predictions
+    or may otherwise be provided as run metadata. Examples include "area_under_roc_curve",
+    "recall", or "usercpu_time_millis". This may be used for filtering or ordering evaluations.
+
+    There are no detailed descriptions available for these measures at this time.
+    """
     functions = await database.evaluations.get_math_functions(
         function_type="EvaluationFunction",
         connection=expdb,
diff --git a/src/routers/openml/flows.py b/src/routers/flows.py
similarity index 91%
rename from src/routers/openml/flows.py
rename to src/routers/flows.py
index b3c3f219..0bb02cb7 100644
--- a/src/routers/openml/flows.py
+++ b/src/routers/flows.py
@@ -1,13 +1,15 @@
+"""Defines endpoints relating to Flows."""
+
 import asyncio
 from typing import TYPE_CHECKING, Annotated, Literal
 
 from fastapi import APIRouter, Depends
 
 import database.flows
-from core.conversions import _str_to_num
+from core.conversions import str_to_num
 from core.errors import FlowNotFoundError
+from core.types import Identifier
 from routers.dependencies import expdb_connection
-from routers.types import Identifier
 from schemas.flows import Flow, Parameter, Subflow
 
 if TYPE_CHECKING:
@@ -39,6 +41,7 @@ async def get_flow(
     flow_id: Identifier,
     expdb: Annotated[AsyncConnection, Depends(expdb_connection)],
 ) -> Flow:
+    """Get a Flow by its identifier."""
     flow = await database.flows.get(flow_id, expdb)
     if not flow:
         msg = f"Flow with id {flow_id} not found."
@@ -55,7 +58,7 @@ async def get_flow(
             # PHP sets the default value to [], not sure where that comes from.
             # In the modern interface, `None` is used instead for now, but I think it might
             # make more sense to omit it if there is none.
-            default_value=_str_to_num(parameter.default_value) if parameter.default_value else None,
+            default_value=str_to_num(parameter.default_value) if parameter.default_value else None,
             data_type=parameter.data_type,
             description=parameter.description,
         )
diff --git a/src/routers/openml/__init__.py b/src/routers/openml/__init__.py
deleted file mode 100644
index 5d924fcf..00000000
--- a/src/routers/openml/__init__.py
+++ /dev/null
@@ -1 +0,0 @@
-"""Routers for the OpenML API."""
diff --git a/src/routers/openml/qualities.py b/src/routers/qualities.py
similarity index 78%
rename from src/routers/openml/qualities.py
rename to src/routers/qualities.py
index dc7a3f55..58d08e69 100644
--- a/src/routers/openml/qualities.py
+++ b/src/routers/qualities.py
@@ -1,20 +1,26 @@
+"""Defines endpoints relating to Qualities.
+
+Qualities are computed meta-features of datasets, such as the number of rows or columns.
+Qualities are computed automatically by an evaluation engine, they are not provided by users.
+"""
+
 from typing import TYPE_CHECKING, Annotated, Literal
 
 from fastapi import APIRouter, Depends
 
 import database.datasets
 import database.qualities
-from core.access import _user_has_access
+from core.access import user_has_access
 from core.errors import (
     DatasetNotFoundError,
     DatasetNotProcessedError,
     DatasetProcessingError,
     NoQualitiesError,
 )
+from core.types import Identifier
 from database.users import User
 from routers.dependencies import expdb_connection, fetch_user
-from routers.types import Identifier
-from schemas.datasets.openml import Quality
+from schemas.datasets import Quality
 
 if TYPE_CHECKING:
     from sqlalchemy.ext.asyncio import AsyncConnection
@@ -26,6 +32,7 @@
 async def list_qualities(
     expdb: Annotated[AsyncConnection, Depends(expdb_connection)],
 ) -> dict[Literal["data_qualities_list"], dict[Literal["quality"], list[str]]]:
+    """List names of all computed qualities (dataset metafeatures)."""
     qualities = await database.qualities.list_all_qualities(connection=expdb)
     return {
         "data_qualities_list": {
@@ -40,8 +47,9 @@ async def get_qualities(
     user: Annotated[User | None, Depends(fetch_user)],
     expdb: Annotated[AsyncConnection, Depends(expdb_connection)],
 ) -> list[Quality]:
+    """Get computed qualities (metafeatures) for a dataset."""
     dataset = await database.datasets.get(dataset_id, expdb)
-    if not dataset or not await _user_has_access(dataset, user):
+    if not dataset or not await user_has_access(dataset, user):
         msg = f"Dataset with id {dataset_id} not found."
         raise DatasetNotFoundError(
             msg,
diff --git a/src/routers/openml/runs.py b/src/routers/runs.py
similarity index 93%
rename from src/routers/openml/runs.py
rename to src/routers/runs.py
index 3869df8d..8484b5e2 100644
--- a/src/routers/openml/runs.py
+++ b/src/routers/runs.py
@@ -1,4 +1,4 @@
-"""Endpoints for run-related data."""
+"""Endpoints relating to Runs and Traces."""
 
 import asyncio
 from dataclasses import dataclass
@@ -13,10 +13,10 @@
 import database.tasks
 import database.users
 from core.errors import RunNotFoundError, RunTraceNotFoundError
-from database.schema.base import UntypedRow
-from database.schema.setups import Setup
+from core.types import Identifier
+from database.models.base import UntypedRow
+from database.models.setups import Setup
 from routers.dependencies import expdb_connection, expdb_session, userdb_connection
-from routers.types import Identifier
 from schemas.runs import (
     EvaluationScore,
     InputDataset,
@@ -149,11 +149,10 @@ async def get_run(
     userdb: Annotated[AsyncConnection, Depends(userdb_connection)],
     expdb_session: Annotated[AsyncSession, Depends(expdb_session)],
 ) -> Run:
-    """Get full metadata for a run by ID.
-
-    No authentication or visibility check is performed — all runs are
-    publicly accessible.
-    """
+    """Get full metadata for a run by ID."""
+    # Authentication is not required because runs are always public.
+    # This mimics PHP API behavior, but is unintuitive for runs which have predictions
+    # made on private datasets.
     run = await database.runs.get(run_id, expdb)
     if run is None:
         msg = f"Run {run_id} not found."
diff --git a/src/routers/openml/setups.py b/src/routers/setups.py
similarity index 95%
rename from src/routers/openml/setups.py
rename to src/routers/setups.py
index d7d86949..c91f3f62 100644
--- a/src/routers/openml/setups.py
+++ b/src/routers/setups.py
@@ -1,4 +1,4 @@
-"""All endpoints that relate to setups."""
+"""Defines endpoints relating to Setups."""
 
 from typing import TYPE_CHECKING, Annotated
 
@@ -12,10 +12,10 @@
     TagNotFoundError,
     TagNotOwnedError,
 )
+from core.types import Identifier, TagString
 from database.exceptions import DuplicatePrimaryKeyError, ForeignKeyConstraintError
 from database.users import User
 from routers.dependencies import expdb_connection, expdb_session, fetch_user_or_raise
-from routers.types import Identifier, TagString
 from schemas.setups import SetupParameters, SetupResponse
 
 if TYPE_CHECKING:
@@ -54,7 +54,7 @@ async def tag_setup(
     user: Annotated[User, Depends(fetch_user_or_raise)],
     expdb_session: Annotated[AsyncSession, Depends(expdb_session)],
 ) -> dict[str, dict[str, str | list[str]]]:
-    """Add tag `tag` to setup with id `setup_id`."""
+    """Add a tag to the setup, this tag is publicly visible to all users."""
     try:
         await database.setups.tag(setup_id, tag, user.user_id, expdb_session)
     except ForeignKeyConstraintError:
diff --git a/src/routers/openml/study.py b/src/routers/study.py
similarity index 93%
rename from src/routers/openml/study.py
rename to src/routers/study.py
index dbb65812..a6869296 100644
--- a/src/routers/openml/study.py
+++ b/src/routers/study.py
@@ -1,3 +1,5 @@
+"""Defines endpoints relating to studies."""
+
 from typing import TYPE_CHECKING, Annotated, Literal
 
 from fastapi import APIRouter, Body, Depends
@@ -15,11 +17,11 @@
     StudyNotFoundError,
     StudyPrivateError,
 )
-from core.formatting import _str_to_bool
-from database.schema.base import UntypedRow
+from core.formatting import str_to_bool
+from core.types import Identifier
+from database.models.base import UntypedRow
 from database.users import User
 from routers.dependencies import expdb_connection, fetch_user, fetch_user_or_raise
-from routers.types import Identifier
 from schemas.core import Visibility
 from schemas.study import CreateStudy, Study, StudyStatus, StudyType
 
@@ -51,13 +53,15 @@ async def _get_study_raise_otherwise(
         if study.creator != user.user_id and not await user.is_admin():
             msg = "Study is private."
             raise StudyPrivateError(msg)
-    if _str_to_bool(study.legacy):
+    if str_to_bool(study.legacy):
         msg = "Legacy studies are no longer supported."
         raise StudyLegacyError(msg)
     return study
 
 
 class AttachDetachResponse(BaseModel):
+    """Response format for attaching or detaching an entity from a study."""
+
     study_id: int
     main_entity_type: StudyType
 
@@ -69,7 +73,7 @@ async def attach_to_study(
     user: Annotated[User, Depends(fetch_user_or_raise)],
     expdb: Annotated[AsyncConnection, Depends(expdb_connection)],
 ) -> AttachDetachResponse:
-    assert expdb is not None  # noqa: S101
+    """Add runs or tasks to a study which is in preparation."""
     if user is None:
         msg = "Authentication required."
         raise AuthenticationRequiredError(msg)
@@ -123,7 +127,7 @@ async def create_study(
     user: Annotated[User, Depends(fetch_user_or_raise)],
     expdb: Annotated[AsyncConnection, Depends(expdb_connection)],
 ) -> dict[Literal["study_id"], int]:
-    assert expdb is not None  # noqa: S101
+    """Create a new study."""
     if study.main_entity_type == StudyType.RUN and study.tasks:
         msg = "Cannot create a run study with tasks."
         raise StudyInvalidTypeError(msg)
@@ -160,11 +164,11 @@ async def get_study(
     expdb: Annotated[AsyncConnection, Depends(expdb_connection)],
     user: Annotated[User | None, Depends(fetch_user)] = None,
 ) -> Study:
-    assert expdb is not None  # noqa: S101
+    """Get a study by id or alias."""
     study = await _get_study_raise_otherwise(alias_or_id, user, expdb)
     study_data = await database.studies.get_study_data(study, expdb)
     return Study(
-        _legacy=_str_to_bool(study.legacy),
+        _legacy=str_to_bool(study.legacy),
         id_=study.id,
         name=study.name,
         alias=study.alias,
diff --git a/src/routers/openml/tasks.py b/src/routers/tasks.py
similarity index 97%
rename from src/routers/openml/tasks.py
rename to src/routers/tasks.py
index 55df6197..ae01a301 100644
--- a/src/routers/openml/tasks.py
+++ b/src/routers/tasks.py
@@ -1,3 +1,5 @@
+"""Defines endpoints relating to Tasks."""
+
 import asyncio
 import json
 import re
@@ -13,18 +15,18 @@
 import database.tasks
 from config import get_config
 from core.errors import InternalError, NoResultsError, TagAlreadyExistsError, TaskNotFoundError
-from database.exceptions import DuplicatePrimaryKeyError, ForeignKeyConstraintError
-from database.schema.base import UntypedRow
-from database.users import User
-from routers.dependencies import Pagination, expdb_connection, expdb_session, fetch_user_or_raise
-from routers.types import (
+from core.types import (
     CasualString128,
     Identifier,
     IntegerRange,
     TagString,
     integer_range_regex,
 )
-from schemas.datasets.openml import Task
+from database.exceptions import DuplicatePrimaryKeyError, ForeignKeyConstraintError
+from database.models.base import UntypedRow
+from database.users import User
+from routers.dependencies import Pagination, expdb_connection, expdb_session, fetch_user_or_raise
+from schemas.tasks import Task
 
 if TYPE_CHECKING:
     from sqlalchemy.ext.asyncio import AsyncConnection, AsyncSession
@@ -41,6 +43,7 @@ async def tag_task(
     user: Annotated[User, Depends(fetch_user_or_raise)],
     expdb_session: Annotated[AsyncSession, Depends(expdb_session)],
 ) -> dict[str, dict[str, Any]]:
+    """Add a tag to the task, this tag is publicly visible to all users."""
     try:
         await database.tasks.tag(task_id, tag, user_id=user.user_id, session=expdb_session)
     except ForeignKeyConstraintError:
@@ -59,7 +62,7 @@ async def tag_task(
     }
 
 
-def convert_template_xml_to_json(xml_template: str) -> dict[str, JSON]:
+def _convert_template_xml_to_json(xml_template: str) -> dict[str, JSON]:
     json_template = xmltodict.parse(xml_template.replace("oml:", ""))
     json_str = json.dumps(json_template)
     # To account for the differences between PHP and Python conversions:
@@ -122,7 +125,7 @@ async def fill_template(
         ]
     }
     """
-    json_template = convert_template_xml_to_json(template)
+    json_template = _convert_template_xml_to_json(template)
     return cast(
         "dict[str, JSON]",
         await _fill_json_template(
@@ -453,6 +456,7 @@ async def get_task(
     expdb: Annotated[AsyncConnection, Depends(expdb_connection)],
     expdb_session: Annotated[AsyncSession, Depends(expdb_session)],
 ) -> Task:
+    """Get a task by identifier."""
     if not (task := await database.tasks.get(task_id, expdb)):
         msg = f"Task {task_id} not found."
         raise TaskNotFoundError(msg)
@@ -480,7 +484,7 @@ async def get_task(
         for (name, _), filled in zip(input_templates, filled_templates, strict=True)
     ]
     outputs = [
-        convert_template_xml_to_json(template) | {"name": name}
+        _convert_template_xml_to_json(template) | {"name": name}
         for name, io, required, template in templates
         if io == "output"
     ]
diff --git a/src/routers/openml/tasktype.py b/src/routers/tasktype.py
similarity index 88%
rename from src/routers/openml/tasktype.py
rename to src/routers/tasktype.py
index 7cdba50e..a92348a9 100644
--- a/src/routers/openml/tasktype.py
+++ b/src/routers/tasktype.py
@@ -1,3 +1,9 @@
+"""Defines endpoints for operations relating to task types.
+
+A task type is a prototype for a task that defines the expected input and output for it.
+Examples include Supervised Classification, Supervised Regression, or Clustering.
+"""
+
 import json
 from typing import TYPE_CHECKING, Annotated, Any, Literal, cast
 
@@ -35,6 +41,7 @@ async def list_task_types(
     Literal["task_types"],
     dict[Literal["task_type"], list[dict[str, str | None | list[Any]]]],
 ]:
+    """Return a high level description of all task types."""
     task_types: list[dict[str, str | None | list[Any]]] = [
         _normalize_task_type(ttype) for ttype in await get_task_types(expdb)
     ]
@@ -46,6 +53,7 @@ async def get_task_type(
     task_type_id: int,
     expdb: Annotated[AsyncConnection, Depends(expdb_connection)],
 ) -> dict[Literal["task_type"], dict[str, str | None | list[str] | list[dict[str, str]]]]:
+    """Return a detailed description for the given task type, including expected inputs."""
     task_type_record = await db_get_task_type(task_type_id, expdb)
     if task_type_record is None:
         msg = f"Task type {task_type_id} not found."
diff --git a/src/routers/openml/users.py b/src/routers/users.py
similarity index 98%
rename from src/routers/openml/users.py
rename to src/routers/users.py
index 43ea9bbd..14a900e7 100644
--- a/src/routers/openml/users.py
+++ b/src/routers/users.py
@@ -1,4 +1,4 @@
-"""User account HTTP endpoints."""
+"""Defines endpoints relating to Users."""
 
 from http import HTTPStatus
 from typing import Annotated
diff --git a/src/schemas/core.py b/src/schemas/core.py
index 77287de5..b9bcb5e6 100644
--- a/src/schemas/core.py
+++ b/src/schemas/core.py
@@ -1,6 +1,16 @@
 from enum import StrEnum, auto
+from typing import NotRequired, TypedDict
+
+from core.types import TagString
 
 
 class Visibility(StrEnum):
     PUBLIC = auto()
     PRIVATE = auto()
+
+
+class TagInfo(TypedDict):
+    """Common PHP response format for tag operations."""
+
+    id: str
+    tag: NotRequired[TagString | list[TagString]]
diff --git a/src/schemas/datasets/openml.py b/src/schemas/datasets.py
similarity index 82%
rename from src/schemas/datasets/openml.py
rename to src/schemas/datasets.py
index 767cbb81..be4795e6 100644
--- a/src/schemas/datasets/openml.py
+++ b/src/schemas/datasets.py
@@ -1,42 +1,59 @@
+"""Defines schemas for API responses relating to Datasets."""
+
 from __future__ import annotations
 
 from datetime import UTC, datetime
 from enum import StrEnum
-from typing import Any
 
 from pydantic import BaseModel, Field, HttpUrl
 
 
 class DatasetFileFormat(StrEnum):
+    """Allowed file formats for data files."""
+
     ARFF = "arff"
     SPARSE_ARFF = "sparse_arff"
     PARQUET = "parquet"
 
 
 class Visibility(StrEnum):
+    """Possible visibility statuses."""
+
     PUBLIC = "public"
     PRIVATE = "private"
 
 
 class DatasetStatus(StrEnum):
+    """Possible dataset statuses.
+
+    - In Preparation: any uploaded dataset isn't yet successfully processed.
+    - Active: any uploaded dataset that has successfully been processed.
+    - Deactivated: use of the dataset is discouraged.
+    """
+
     ACTIVE = "active"
     DEACTIVATED = "deactivated"
-    IN_PROCESSING = "in processing"
     IN_PREPARATION = "in_preparation"
 
 
 class Quality(BaseModel):
+    """A computed quality (meta-feature) of the dataset."""
+
     name: str
     value: float | None
 
 
 class FeatureType(StrEnum):
+    """The type of a feature (column) in the dataset."""
+
     NUMERIC = "numeric"
     NOMINAL = "nominal"
     STRING = "string"
 
 
 class Feature(BaseModel):
+    """Metadata about a feature (column) in the dataset."""
+
     index: int
     name: str
     data_type: FeatureType
@@ -48,18 +65,9 @@ class Feature(BaseModel):
     nominal_values: list[str] | None
 
 
-class EstimationProcedure(BaseModel):
-    id_: int = Field(serialization_alias="id")
-    task_type_id: int
-    name: str
-    type_: str = Field(serialization_alias="type")
-    percentage: int | None
-    repeats: int | None
-    folds: int | None
-    stratified_sampling: bool | None
-
-
 class DatasetMetadata(BaseModel):
+    """Metadata for a dataset."""
+
     id_: int = Field(json_schema_extra={"example": 1}, alias="id")
     visibility: Visibility = Field(json_schema_extra={"example": Visibility.PUBLIC})
     status: DatasetStatus = Field(json_schema_extra={"example": DatasetStatus.ACTIVE})
@@ -134,15 +142,3 @@ class DatasetMetadata(BaseModel):
         json_schema_extra={"example": "https://www.openml.org/d/2"},
     )
     md5_checksum: str = Field(json_schema_extra={"example": "d01f6ccd68c88b749b20bbe897de3713"})
-
-
-class Task(BaseModel):
-    id_: int = Field(serialization_alias="id", json_schema_extra={"example": 59})
-    name: str = Field(
-        json_schema_extra={"example": "Task 59:  mfeat-pixel (Supervised Classification)"},
-    )
-    task_type_id: int = Field(json_schema_extra={"example": 1})
-    task_type: str = Field(json_schema_extra={"example": "Supervised Classification"})
-    input_: list[dict[str, Any]] = Field(serialization_alias="input")
-    output: list[dict[str, Any]]
-    tags: list[str] = Field(default_factory=list)
diff --git a/src/schemas/datasets/__init__.py b/src/schemas/datasets/__init__.py
deleted file mode 100644
index c34a2d8f..00000000
--- a/src/schemas/datasets/__init__.py
+++ /dev/null
@@ -1,9 +0,0 @@
-"""Dataset schemas for the OpenML server API."""
-
-from enum import StrEnum
-
-
-class DatasetSchema(StrEnum):
-    DCAT_AP = "dcat-ap"
-    OPENML = "openml"
-    MLDCAT_AP = "mldcat-ap"
diff --git a/src/schemas/tasks.py b/src/schemas/tasks.py
new file mode 100644
index 00000000..475f1a4c
--- /dev/null
+++ b/src/schemas/tasks.py
@@ -0,0 +1,34 @@
+"""Defines schemas for API responses relating to Tasks."""
+
+from typing import Any
+
+from pydantic import BaseModel, Field
+
+from core.types import Identifier
+
+
+class Task(BaseModel):
+    """Metadata for a task."""
+
+    id_: Identifier = Field(serialization_alias="id", json_schema_extra={"example": 59})
+    name: str = Field(
+        json_schema_extra={"example": "Task 59:  mfeat-pixel (Supervised Classification)"},
+    )
+    task_type_id: Identifier = Field(json_schema_extra={"example": 1})
+    task_type: str = Field(json_schema_extra={"example": "Supervised Classification"})
+    input_: list[dict[str, Any]] = Field(serialization_alias="input")
+    output: list[dict[str, Any]]
+    tags: list[str] = Field(default_factory=list)
+
+
+class EstimationProcedure(BaseModel):
+    """Description of an evaluation protocol, e.g., cross-validation."""
+
+    id_: Identifier = Field(serialization_alias="id")
+    task_type_id: Identifier
+    name: str
+    type_: str = Field(serialization_alias="type")
+    percentage: int | None
+    repeats: int | None
+    folds: int | None
+    stratified_sampling: bool | None
diff --git a/tests/conftest.py b/tests/conftest.py
index 68a8e1cb..ded9c543 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -21,10 +21,10 @@
     LoggingConfiguration,
     RoutingConfiguration,
 )
-from database.setup import expdb_database, user_database
+from core.types import Identifier
+from database.engine import expdb_database, user_database
 from main import create_api
 from routers.dependencies import expdb_connection, userdb_connection
-from routers.types import Identifier
 from tests.users import OWNER_USER
 
 if TYPE_CHECKING:
diff --git a/tests/routers/openml/dataset_tag_test.py b/tests/routers/dataset_tag_test.py
similarity index 96%
rename from tests/routers/openml/dataset_tag_test.py
rename to tests/routers/dataset_tag_test.py
index dd80966d..6c8201fa 100644
--- a/tests/routers/openml/dataset_tag_test.py
+++ b/tests/routers/dataset_tag_test.py
@@ -6,10 +6,10 @@
 from core.errors import DatasetNotFoundError, TagAlreadyExistsError
 from database.datasets import get_tags_for
 from database.users import User
-from routers.openml.datasets import tag_dataset
+from routers.datasets import tag_dataset
 from tests import constants
 from tests.conftest import DatasetFactory
-from tests.routers.openml.tag_test_helper import assert_tag_response_is_identical
+from tests.routers.tag_test_helper import assert_tag_response_is_identical
 from tests.users import ADMIN_USER, OWNER_USER, SOME_USER, ApiKey
 
 if TYPE_CHECKING:
diff --git a/tests/routers/openml/dataset_untag_test.py b/tests/routers/dataset_untag_test.py
similarity index 99%
rename from tests/routers/openml/dataset_untag_test.py
rename to tests/routers/dataset_untag_test.py
index cfaaf249..7eca8893 100644
--- a/tests/routers/openml/dataset_untag_test.py
+++ b/tests/routers/dataset_untag_test.py
@@ -20,7 +20,7 @@
 from sqlalchemy import text
 
 from core.errors import DatasetNotFoundError, TagNotFoundError, TagNotOwnedError
-from routers.openml.datasets import untag_dataset
+from routers.datasets import untag_dataset
 from tests.users import ADMIN_USER, SOME_USER, ApiKey
 
 if TYPE_CHECKING:
diff --git a/tests/routers/openml/datasets_features_test.py b/tests/routers/datasets_features_test.py
similarity index 99%
rename from tests/routers/openml/datasets_features_test.py
rename to tests/routers/datasets_features_test.py
index 36166596..f4e56d2c 100644
--- a/tests/routers/openml/datasets_features_test.py
+++ b/tests/routers/datasets_features_test.py
@@ -9,7 +9,7 @@
 
 from core.errors import DatasetNoAccessError, DatasetNotFoundError, DatasetProcessingError
 from database.users import User
-from routers.openml.datasets import get_dataset_features
+from routers.datasets import get_dataset_features
 from tests.users import ADMIN_USER, DATASET_130_OWNER
 
 if TYPE_CHECKING:
diff --git a/tests/routers/openml/datasets_get_test.py b/tests/routers/datasets_get_test.py
similarity index 98%
rename from tests/routers/openml/datasets_get_test.py
rename to tests/routers/datasets_get_test.py
index 3ef034eb..cf38c0dc 100644
--- a/tests/routers/openml/datasets_get_test.py
+++ b/tests/routers/datasets_get_test.py
@@ -12,8 +12,8 @@
 import tests.constants
 from core.errors import DatasetNoAccessError, DatasetNotFoundError
 from database.users import User
-from routers.openml.datasets import get_dataset
-from schemas.datasets.openml import DatasetMetadata
+from routers.datasets import get_dataset
+from schemas.datasets import DatasetMetadata
 from tests.users import ADMIN_USER, DATASET_130_OWNER, NO_USER, SOME_USER, ApiKey
 
 if TYPE_CHECKING:
diff --git a/tests/routers/openml/datasets_list_datasets_test.py b/tests/routers/datasets_list_datasets_test.py
similarity index 99%
rename from tests/routers/openml/datasets_list_datasets_test.py
rename to tests/routers/datasets_list_datasets_test.py
index 868e9ee6..89ec474f 100644
--- a/tests/routers/openml/datasets_list_datasets_test.py
+++ b/tests/routers/datasets_list_datasets_test.py
@@ -10,8 +10,8 @@
 
 from core.errors import NoResultsError
 from database.users import User
+from routers.datasets import DatasetStatusFilter, list_datasets
 from routers.dependencies import LIMIT_DEFAULT, Pagination
-from routers.openml.datasets import DatasetStatusFilter, list_datasets
 from tests import constants
 from tests.users import ADMIN_USER, DATASET_130_OWNER, SOME_USER, ApiKey
 
diff --git a/tests/routers/openml/datasets_qualities_test.py b/tests/routers/datasets_qualities_test.py
similarity index 100%
rename from tests/routers/openml/datasets_qualities_test.py
rename to tests/routers/datasets_qualities_test.py
diff --git a/tests/routers/openml/datasets_status_test.py b/tests/routers/datasets_status_test.py
similarity index 96%
rename from tests/routers/openml/datasets_status_test.py
rename to tests/routers/datasets_status_test.py
index adc5892e..581465a2 100644
--- a/tests/routers/openml/datasets_status_test.py
+++ b/tests/routers/datasets_status_test.py
@@ -6,8 +6,8 @@
 import pytest
 
 from core.errors import DatasetAdminOnlyError, DatasetNotOwnedError
-from routers.openml.datasets import update_dataset_status
-from schemas.datasets.openml import DatasetStatus
+from routers.datasets import update_dataset_status
+from schemas.datasets import DatasetStatus
 from tests import constants
 from tests.users import ADMIN_USER, SOME_USER
 
diff --git a/tests/routers/openml/estimation_procedure_test.py b/tests/routers/estimation_procedure_test.py
similarity index 100%
rename from tests/routers/openml/estimation_procedure_test.py
rename to tests/routers/estimation_procedure_test.py
diff --git a/tests/routers/openml/evaluation_measure_test.py b/tests/routers/evaluation_measure_test.py
similarity index 100%
rename from tests/routers/openml/evaluation_measure_test.py
rename to tests/routers/evaluation_measure_test.py
diff --git a/tests/routers/openml/flows_exists_test.py b/tests/routers/flows_exists_test.py
similarity index 98%
rename from tests/routers/openml/flows_exists_test.py
rename to tests/routers/flows_exists_test.py
index 988402f3..c5889412 100644
--- a/tests/routers/openml/flows_exists_test.py
+++ b/tests/routers/flows_exists_test.py
@@ -6,7 +6,7 @@
 import pytest
 
 from core.errors import FlowNotFoundError
-from routers.openml.flows import flow_exists
+from routers.flows import flow_exists
 from tests.conftest import Flow
 
 if TYPE_CHECKING:
diff --git a/tests/routers/openml/flows_get_test.py b/tests/routers/flows_get_test.py
similarity index 100%
rename from tests/routers/openml/flows_get_test.py
rename to tests/routers/flows_get_test.py
diff --git a/tests/routers/openml/__init__.py b/tests/routers/openml/__init__.py
deleted file mode 100644
index e69de29b..00000000
diff --git a/tests/routers/openml/qualities_list_test.py b/tests/routers/qualities_list_test.py
similarity index 100%
rename from tests/routers/openml/qualities_list_test.py
rename to tests/routers/qualities_list_test.py
diff --git a/tests/routers/openml/runs_get_test.py b/tests/routers/runs_get_test.py
similarity index 97%
rename from tests/routers/openml/runs_get_test.py
rename to tests/routers/runs_get_test.py
index af841f65..f9d897c5 100644
--- a/tests/routers/openml/runs_get_test.py
+++ b/tests/routers/runs_get_test.py
@@ -10,7 +10,7 @@
 import pytest
 
 from core.conversions import nested_num_to_str, nested_remove_single_element_list
-from routers.openml.runs import _build_evaluations
+from routers.runs import _build_evaluations
 
 # ── Fixtures assume run 24 exists in the test DB (confirmed in research) ──
 _RUN_ID = 24
@@ -149,7 +149,7 @@ class MockRunRow(NamedTuple):
         error_message="Some error from the backend",
     )
 
-    with patch("routers.openml.runs.database.runs.get", new_callable=AsyncMock) as mock_get:
+    with patch("routers.runs.database.runs.get", new_callable=AsyncMock) as mock_get:
         mock_get.return_value = mock_row
         response = await py_api.get(f"/run/{_RUN_ID}")
         assert response.status_code == HTTPStatus.OK
@@ -181,7 +181,7 @@ async def test_task_evaluation_measure_present_when_configured(
     """task_evaluation_measure is present and matches DB when a measure is configured."""
     # Since the test database does not have a run with an evaluation measure, we mock the DB fetch
     with patch(
-        "routers.openml.runs.database.tasks.get_task_evaluation_measure", new_callable=AsyncMock
+        "routers.runs.database.tasks.get_task_evaluation_measure", new_callable=AsyncMock
     ) as mock_get_measure:
         mock_get_measure.return_value = "predictive_accuracy"
         response = await py_api.get(f"/run/{_RUN_ID}")
diff --git a/tests/routers/openml/runs_trace_test.py b/tests/routers/runs_trace_test.py
similarity index 100%
rename from tests/routers/openml/runs_trace_test.py
rename to tests/routers/runs_trace_test.py
diff --git a/tests/routers/openml/setups_get_test.py b/tests/routers/setups_get_test.py
similarity index 100%
rename from tests/routers/openml/setups_get_test.py
rename to tests/routers/setups_get_test.py
diff --git a/tests/routers/openml/setups_tag_test.py b/tests/routers/setups_tag_test.py
similarity index 99%
rename from tests/routers/openml/setups_tag_test.py
rename to tests/routers/setups_tag_test.py
index 60488c24..49bad891 100644
--- a/tests/routers/openml/setups_tag_test.py
+++ b/tests/routers/setups_tag_test.py
@@ -9,7 +9,7 @@
 from sqlalchemy import text
 
 from core.errors import SetupNotFoundError, TagAlreadyExistsError
-from routers.openml.setups import tag_setup
+from routers.setups import tag_setup
 from tests.users import SOME_USER, ApiKey
 
 if TYPE_CHECKING:
diff --git a/tests/routers/openml/setups_untag_test.py b/tests/routers/setups_untag_test.py
similarity index 99%
rename from tests/routers/openml/setups_untag_test.py
rename to tests/routers/setups_untag_test.py
index c4424f16..1259f1e0 100644
--- a/tests/routers/openml/setups_untag_test.py
+++ b/tests/routers/setups_untag_test.py
@@ -9,7 +9,7 @@
 from sqlalchemy import text
 
 from core.errors import SetupNotFoundError, TagNotFoundError, TagNotOwnedError
-from routers.openml.setups import untag_setup
+from routers.setups import untag_setup
 from tests.users import ADMIN_USER, OWNER_USER, SOME_USER, ApiKey
 
 if TYPE_CHECKING:
diff --git a/tests/routers/openml/study_attach_test.py b/tests/routers/study_attach_test.py
similarity index 100%
rename from tests/routers/openml/study_attach_test.py
rename to tests/routers/study_attach_test.py
diff --git a/tests/routers/openml/study_get_test.py b/tests/routers/study_get_test.py
similarity index 100%
rename from tests/routers/openml/study_get_test.py
rename to tests/routers/study_get_test.py
diff --git a/tests/routers/openml/study_post_test.py b/tests/routers/study_post_test.py
similarity index 100%
rename from tests/routers/openml/study_post_test.py
rename to tests/routers/study_post_test.py
diff --git a/tests/routers/openml/tag_test_helper.py b/tests/routers/tag_test_helper.py
similarity index 100%
rename from tests/routers/openml/tag_test_helper.py
rename to tests/routers/tag_test_helper.py
diff --git a/tests/routers/openml/task_get_test.py b/tests/routers/task_get_test.py
similarity index 100%
rename from tests/routers/openml/task_get_test.py
rename to tests/routers/task_get_test.py
diff --git a/tests/routers/openml/task_list_test.py b/tests/routers/task_list_test.py
similarity index 99%
rename from tests/routers/openml/task_list_test.py
rename to tests/routers/task_list_test.py
index 7a3f562f..01443e10 100644
--- a/tests/routers/openml/task_list_test.py
+++ b/tests/routers/task_list_test.py
@@ -8,7 +8,7 @@
 from core.conversions import nested_remove_single_element_list
 from core.errors import NoResultsError
 from routers.dependencies import LIMIT_MAX, Pagination
-from routers.openml.tasks import TaskStatusFilter, list_tasks
+from routers.tasks import TaskStatusFilter, list_tasks
 
 if TYPE_CHECKING:
     import httpx
diff --git a/tests/routers/openml/task_tag_test.py b/tests/routers/task_tag_test.py
similarity index 96%
rename from tests/routers/openml/task_tag_test.py
rename to tests/routers/task_tag_test.py
index f6e04b10..8ad52b60 100644
--- a/tests/routers/openml/task_tag_test.py
+++ b/tests/routers/task_tag_test.py
@@ -6,10 +6,10 @@
 from core.errors import TASK_NOT_FOUND_DURING_TAG, TagAlreadyExistsError, TaskNotFoundError
 from database.tasks import get_tags
 from database.users import User
-from routers.openml.tasks import tag_task
+from routers.tasks import tag_task
 from tests import constants
 from tests.conftest import TaskFactory
-from tests.routers.openml.tag_test_helper import assert_tag_response_is_identical
+from tests.routers.tag_test_helper import assert_tag_response_is_identical
 from tests.users import ADMIN_USER, OWNER_USER, SOME_USER, ApiKey
 
 if TYPE_CHECKING:
diff --git a/tests/routers/openml/task_type_get_test.py b/tests/routers/task_type_get_test.py
similarity index 100%
rename from tests/routers/openml/task_type_get_test.py
rename to tests/routers/task_type_get_test.py
diff --git a/tests/routers/openml/task_type_list_test.py b/tests/routers/task_type_list_test.py
similarity index 100%
rename from tests/routers/openml/task_type_list_test.py
rename to tests/routers/task_type_list_test.py
diff --git a/tests/routers/openml/users_delete_test.py b/tests/routers/users_delete_test.py
similarity index 97%
rename from tests/routers/openml/users_delete_test.py
rename to tests/routers/users_delete_test.py
index 127e89e7..c872c747 100644
--- a/tests/routers/openml/users_delete_test.py
+++ b/tests/routers/users_delete_test.py
@@ -13,7 +13,7 @@
 
 from core.errors import AccountHasResourcesError, ForbiddenError, UserNotFoundError
 from database.users import UserGroup
-from routers.openml.users import delete_user_account
+from routers.users import delete_user_account
 from tests.users import ADMIN_USER, OWNER_USER, SOME_USER, ApiKey
 
 
@@ -69,7 +69,7 @@ async def test_delete_user_api_success_self_delete(
     disposable_user: DisposableUser,
     mocker: pytest_mock.MockerFixture,
 ) -> None:
-    log_info = mocker.patch("routers.openml.users.logger.info")
+    log_info = mocker.patch("routers.users.logger.info")
 
     response = await py_api.delete(
         f"/users/{disposable_user.user_id}",
@@ -185,7 +185,7 @@ async def test_delete_user_integrity_error_logs_and_raises_conflict(
             "DELETE FROM users", {"user_id": disposable_user.user_id}, Exception("fk")
         ),
     )
-    log_error = mocker.patch("routers.openml.users.logger.error")
+    log_error = mocker.patch("routers.users.logger.error")
 
     with pytest.raises(AccountHasResourcesError, match="Cannot delete this account") as exc_info:
         await delete_user_account(
diff --git a/tests/types_test.py b/tests/types_test.py
index 7a4df612..2ded54c1 100644
--- a/tests/types_test.py
+++ b/tests/types_test.py
@@ -11,7 +11,7 @@
 import pytest
 from pydantic import TypeAdapter, ValidationError
 
-from routers.types import CasualString, Identifier, TagString
+from core.types import CasualString, Identifier, TagString
 
 _identifier = TypeAdapter(Identifier)