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fix: update MergeAgentHandlerTool to rightly handle MCP protocol #4255

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fix: update MergeAgentHandlerTool to rightly handle MCP protocol #4255

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fix: update MergeAgentHandlerTool to handle Agent Handler MCP protoco…
mplacona Jan 20, 2026
e3ee442
fix(merge-tool): correct required nullable field handling
mplacona Jan 20, 2026
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mplacona Jan 21, 2026
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lorenzejay Jan 27, 2026
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lorenzejay Jan 27, 2026
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lorenzejay Jan 28, 2026
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mplacona Jan 28, 2026
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lorenzejay Jan 30, 2026
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mplacona Feb 3, 2026
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lorenzejay Feb 11, 2026
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mplacona Feb 26, 2026
4f22166
fix: resolve schema errors and type bugs in MergeAgentHandlerTool
mplacona Feb 26, 2026
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mplacona Feb 26, 2026
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123 changes: 89 additions & 34 deletions lib/crewai-tools/src/crewai_tools/tools/merge_agent_handler_tool/merge_agent_handler_tool.py
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Original file line number Diff line number Diff line change
Expand Up @@ -6,7 +6,7 @@
from uuid import uuid4

from crewai.tools import BaseTool, EnvVar
from pydantic import BaseModel, Field, create_model
from pydantic import Field, create_model
import requests
import typing_extensions as te

Expand All @@ -18,7 +18,6 @@ class MergeAgentHandlerToolError(Exception):
"""Base exception for Merge Agent Handler tool errors."""



class MergeAgentHandlerTool(BaseTool):
"""
Wrapper for Merge Agent Handler tools.
Expand Down Expand Up @@ -109,7 +108,7 @@ def _make_mcp_request(
)
raise MergeAgentHandlerToolError(f"API Error: {error_msg}")

return result
return result # type: ignore[no-any-return]

except requests.exceptions.RequestException as e:
logger.error(f"Failed to call Agent Handler API: {e!s}")
Expand All @@ -123,10 +122,18 @@ def _run(self, **kwargs: Any) -> Any:
# Log what we're about to send
logger.info(f"Executing {self.tool_name} with arguments: {kwargs}")

# Agent Handler wraps parameters in an "input" object
# If arguments are already wrapped (from workaround), use as-is
# Otherwise, wrap them
if "input" in kwargs and len(kwargs) == 1:
arguments = kwargs
else:
arguments = {"input": kwargs}
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# Make the tool call via MCP
result = self._make_mcp_request(
method="tools/call",
params={"name": self.tool_name, "arguments": kwargs},
params={"name": self.tool_name, "arguments": arguments},
)

# Extract the actual result from the MCP response
Expand Down Expand Up @@ -174,7 +181,7 @@ def from_tool_name(
>>> tool = MergeAgentHandlerTool.from_tool_name(
... tool_name="linear__create_issue",
... tool_pack_id="134e0111-0f67-44f6-98f0-597000290bb3",
... registered_user_id="91b2b905-e866-40c8-8be2-efe53827a0aa"
... registered_user_id="91b2b905-e866-40c8-8be2-efe53827a0aa",
... )
"""
# Create an empty args schema model (proper BaseModel subclass)
Expand Down Expand Up @@ -206,37 +213,78 @@ def from_tool_name(
"description", instance.description
)

# Convert parameters schema to Pydantic model
if "parameters" in tool_schema:
# Convert inputSchema to Pydantic model (MCP protocol uses "inputSchema")
if "inputSchema" in tool_schema:
try:
params = tool_schema["parameters"]
if params.get("type") == "object" and "properties" in params:
# Build field definitions for Pydantic
fields = {}
params = tool_schema["inputSchema"]
if (
params.get("type") == "object"
and "properties" in params
):
# Agent Handler wraps parameters in an "input" object
# Check if we need to unwrap it
properties = params["properties"]
required = params.get("required", [])

if "input" in properties and len(properties) == 1:
# Unwrap the input object to get actual parameters
input_schema = properties["input"]
if (
isinstance(input_schema, dict)
and "properties" in input_schema
):
properties = input_schema["properties"]
required = input_schema.get("required", [])

# Build field definitions for Pydantic
fields = {}

for field_name, field_schema in properties.items():
field_type = Any # Default type
field_default = ... # Required by default

# Map JSON schema types to Python types
json_type = field_schema.get("type", "string")
if json_type == "string":
field_type = str
elif json_type == "integer":
field_type = int
elif json_type == "number":
field_type = float
elif json_type == "boolean":
field_type = bool
elif json_type == "array":
field_type = list[Any]
elif json_type == "object":
field_type = dict[str, Any]

# Make field optional if not required
if field_name not in required:
field_type: Any = Any # Default type
field_default: Any = ... # Required by default
is_nullable = False

# Check if field uses anyOf (common for nullable types)
if "anyOf" in field_schema:
# anyOf typically means the field can be null
types_in_any_of = field_schema["anyOf"]
for type_def in types_in_any_of:
if isinstance(type_def, dict):
if type_def.get("type") == "null":
is_nullable = True
elif "type" in type_def:
# Use the non-null type
json_type = type_def["type"]
if json_type == "string":
field_type = str
elif json_type == "integer":
field_type = int
elif json_type == "number":
field_type = float
elif json_type == "boolean":
field_type = bool
elif json_type == "array":
field_type = list[Any]
elif json_type == "object":
field_type = dict[str, Any]
else:
# Map JSON schema types to Python types
json_type = field_schema.get("type", "string")
if json_type == "string":
field_type = str
elif json_type == "integer":
field_type = int
elif json_type == "number":
field_type = float
elif json_type == "boolean":
field_type = bool
elif json_type == "array":
field_type = list[Any]
elif json_type == "object":
field_type = dict[str, Any]
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# Make field optional if not required or if nullable
if field_name not in required or is_nullable:
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field_type = field_type | None
field_default = None

Expand All @@ -254,7 +302,7 @@ def from_tool_name(

# Create the Pydantic model
if fields:
args_schema = create_model(
args_schema = create_model( # type: ignore[call-overload]
f"{tool_name.replace('__', '_').title()}Args",
**fields,
)
Expand All @@ -264,6 +312,12 @@ def from_tool_name(
logger.warning(
f"Failed to create args schema for {tool_name}: {e!s}"
)
else:
# Log when inputSchema is missing to help debugging
logger.debug(
f"Tool {tool_name} has no inputSchema in response. "
f"Available keys: {list(tool_schema.keys())}"
)

except Exception as e:
logger.warning(
Expand Down Expand Up @@ -298,18 +352,19 @@ def from_tool_pack(
>>> tools = MergeAgentHandlerTool.from_tool_pack(
... tool_pack_id="134e0111-0f67-44f6-98f0-597000290bb3",
... registered_user_id="91b2b905-e866-40c8-8be2-efe53827a0aa",
... tool_names=["linear__create_issue", "linear__get_issues"]
... tool_names=["linear__create_issue", "linear__get_issues"],
... )
"""
# Create a temporary instance to fetch the tool list
temp_args_schema = create_model("TempArgs")
temp_instance = cls(
name="temp",
description="temp",
tool_pack_id=tool_pack_id,
registered_user_id=registered_user_id,
tool_name="temp",
base_url=base_url,
args_schema=BaseModel,
args_schema=temp_args_schema,
)

try:
Expand Down
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