feat: add mcp_resource_trigger (#312)

* Add mcp_resource_trigger

* lint

* fix pipeline

* add metadata property to mcp_tool

Author: hallvictoria

azure/functions/decorators/constants.py

@@ -46,3 +46,4 @@
 MYSQL = "mysql"
 MYSQL_TRIGGER = "mysqlTrigger"
 MCP_TOOL_TRIGGER = "mcpToolTrigger"
+MCP_RESOURCE_TRIGGER = "mcpResourceTrigger"

azure/functions/decorators/function_app.py

@@ -47,7 +47,7 @@
     _AssistantQueryInput, _AssistantPostInput, InputType, _EmbeddingsInput, \
     semantic_search_system_prompt, \
     _SemanticSearchInput, _EmbeddingsStoreOutput
-from .mcp import _MCPToolTrigger, build_property_metadata
+from .mcp import _MCPToolTrigger, MCPResourceTrigger, build_property_metadata
 from .retry_policy import RetryPolicy
 from .function_name import FunctionName
 from .warmup import WarmUpTrigger
@@ -1576,7 +1576,7 @@ def decorator():
 
         return wrap
 
-    def mcp_tool(self):
+    def mcp_tool(self, metadata: Optional[str] = None):
         """Decorator to register an MCP tool function.
         Ref: https://aka.ms/remote-mcp-functions-python
 
@@ -1585,6 +1585,8 @@ def mcp_tool(self):
         - Extracts docstrings as description
         - Extracts parameters and types for tool properties
         - Handles MCPToolContext injection
+
+        :param metadata: JSON-serialized metadata object for the tool.
         """
         @self._configure_function_builder
         def decorator(fb: FunctionBuilder) -> FunctionBuilder:
@@ -1649,6 +1651,7 @@ async def wrapper(context: str, *args, **kwargs):
                     tool_name=tool_name,
                     description=description,
                     tool_properties=tool_properties_json,
+                    metadata=metadata
                 )
             )
             return fb
@@ -1689,6 +1692,68 @@ def decorator(func):
             return func
         return decorator
 
+    def mcp_resource_trigger(self,
+                             arg_name: str,
+                             uri: str,
+                             resource_name: str,
+                             title: Optional[str] = None,
+                             description: Optional[str] = None,
+                             mime_type: Optional[str] = None,
+                             size: Optional[int] = None,
+                             metadata: Optional[str] = None,
+                             data_type: Optional[Union[DataType, str]] = None,
+                             **kwargs) -> Callable[..., Any]:
+        """The `mcp_resource_trigger` decorator adds :class:`MCPResourceTrigger` to the
+        :class:`FunctionBuilder` object for building a :class:`Function` object
+        used in the worker function indexing model.
+
+        This is equivalent to defining `MCPResourceTrigger` in the `function.json`,
+        which enables the function to be triggered when MCP resource requests are
+        received by the host.
+
+        All optional fields will be given default values by the function host when
+        they are parsed.
+
+        Ref: https://aka.ms/remote-mcp-functions-python
+
+        :param arg_name: The name of the trigger parameter in the function code.
+        :param uri: Unique URI identifier for the resource (must be absolute).
+        :param resource_name: Human-readable name of the resource.
+        :param title: Optional title for display purposes.
+        :param description: Optional description of the resource.
+        :param mime_type: Optional MIME type of the resource content.
+        :param size: Optional size of the resource in bytes.
+        :param metadata: Optional JSON-serialized metadata object.
+        :param data_type: Defines how the Functions runtime should treat the
+            parameter value.
+        :param kwargs: Keyword arguments for specifying additional binding
+            fields to include in the binding JSON.
+
+        :return: Decorator function.
+        """
+
+        @self._configure_function_builder
+        def wrap(fb):
+            def decorator():
+                fb.add_trigger(
+                    trigger=MCPResourceTrigger(
+                        name=arg_name,
+                        uri=uri,
+                        resource_name=resource_name,
+                        title=title,
+                        description=description,
+                        mime_type=mime_type,
+                        size=size,
+                        metadata=metadata,
+                        data_type=parse_singular_param_to_enum(data_type,
+                                                               DataType),
+                        **kwargs))
+                return fb
+
+            return decorator()
+
+        return wrap
+
     def dapr_service_invocation_trigger(self,
                                         arg_name: str,
                                         method_name: str,

azure/functions/decorators/mcp.py

@@ -7,7 +7,7 @@
 
 from ..mcp import MCPToolContext
 from azure.functions.decorators.constants import (
-    MCP_TOOL_TRIGGER
+    MCP_TOOL_TRIGGER, MCP_RESOURCE_TRIGGER
 )
 from azure.functions.decorators.core import Trigger, DataType, McpPropertyType
 
@@ -22,6 +22,33 @@
 }
 
 
+class MCPResourceTrigger(Trigger):
+
+    @staticmethod
+    def get_binding_name() -> str:
+        return MCP_RESOURCE_TRIGGER
+
+    def __init__(self,
+                 name: str,
+                 uri: str,
+                 resource_name: str,
+                 title: Optional[str] = None,
+                 description: Optional[str] = None,
+                 mime_type: Optional[str] = None,
+                 size: Optional[int] = None,
+                 metadata: Optional[str] = None,
+                 data_type: Optional[DataType] = None,
+                 **kwargs):
+        self.uri = uri
+        self.resourceName = resource_name
+        self.title = title
+        self.description = description
+        self.mimeType = mime_type
+        self.size = size
+        self.metadata = metadata
+        super().__init__(name=name, data_type=data_type)
+
+
 class _MCPToolTrigger(Trigger):
 
     @staticmethod
@@ -33,11 +60,13 @@ def __init__(self,
                  tool_name: str,
                  description: Optional[str] = None,
                  tool_properties: Optional[str] = None,
+                 metadata: Optional[str] = None,
                  data_type: Optional[DataType] = None,
                  **kwargs):
         self.tool_name = tool_name
         self.description = description
         self.tool_properties = tool_properties
+        self.metadata = metadata
         super().__init__(name=name, data_type=data_type)
 
 

azure/functions/mcp.py

@@ -57,3 +57,50 @@ def encode(cls, obj: typing.Any, *, expected_type: typing.Optional[type] = None)
         else:
             # Convert other types to string
             return meta.Datum(type='string', value=str(obj))
+
+
+class MCPResourceTriggerConverter(meta.InConverter, binding='mcpResourceTrigger',
+                                  trigger=True):
+
+    @classmethod
+    def check_input_type_annotation(cls, pytype: type) -> bool:
+        return issubclass(pytype, (str, dict, bytes))
+
+    @classmethod
+    def has_implicit_output(cls) -> bool:
+        return True
+
+    @classmethod
+    def decode(cls, data: meta.Datum, *, trigger_metadata):
+        """
+        Decode incoming MCP resource request data.
+        Returns the raw data in its native format (string, dict, bytes).
+        """
+        # Handle different data types appropriately
+        if data.type == 'json':
+            # If it's already parsed JSON, use the value directly
+            return data.value
+        elif data.type == 'string':
+            # If it's a string, use it as-is
+            return data.value
+        elif data.type == 'bytes':
+            return data.value
+        else:
+            # Fallback to python_value for other types
+            return data.python_value if hasattr(data, 'python_value') else data.value
+
+    @classmethod
+    def encode(cls, obj: typing.Any, *, expected_type: typing.Optional[type] = None):
+        """
+        Encode the return value from MCP resource functions.
+        MCP resources typically return string responses.
+        """
+        if obj is None:
+            return meta.Datum(type='string', value='')
+        elif isinstance(obj, str):
+            return meta.Datum(type='string', value=obj)
+        elif isinstance(obj, (bytes, bytearray)):
+            return meta.Datum(type='bytes', value=bytes(obj))
+        else:
+            # Convert other types to string
+            return meta.Datum(type='string', value=str(obj))

eng/templates/official/jobs/publish-release.yml

@@ -80,7 +80,7 @@ jobs:
           exit -1
       }
     displayName: 'Tag and push x.y.z'
-  - powershell: |
+  - pwsh: |
       $githubUser = "$(GithubUser)"
       $githubToken = "$(GithubPat)"
       $newLibraryVersion = "$(NewLibraryVersion)"
@@ -123,7 +123,7 @@ jobs:
   dependsOn: ['CheckGitHubRelease']
   displayName: 'Test with Worker'
   steps:
-  - powershell: |
+  - pwsh: |
       $githubUser = "$(GithubUser)"
       $githubToken = "$(GithubPat)"
       $newLibraryVersion = "$(NewLibraryVersion)"
@@ -203,7 +203,7 @@ jobs:
     displayName: 'Use Python 3.11'
     inputs:
       versionSpec: 3.11
-  - powershell: |
+  - pwsh: |
       $newLibraryVersion = "$(NewLibraryVersion)"
       $pypiToken = "$(PypiToken)"
       

tests/decorators/test_mcp.py

@@ -6,8 +6,8 @@
 import azure.functions as func
 from azure.functions import DataType, MCPToolContext
 from azure.functions.decorators.core import BindingDirection
-from azure.functions.decorators.mcp import _MCPToolTrigger
-from azure.functions.mcp import _MCPToolTriggerConverter
+from azure.functions.decorators.mcp import _MCPToolTrigger, MCPResourceTrigger
+from azure.functions.mcp import _MCPToolTriggerConverter, MCPResourceTriggerConverter
 from azure.functions.meta import Datum
 
 
@@ -18,6 +18,7 @@ def test_mcp_tool_trigger_valid_creation(self):
             tool_name="hello",
             description="Hello world.",
             tool_properties="[]",
+            metadata='{"key": "value"}',
             data_type=DataType.UNDEFINED,
             dummy_field="dummy",
         )
@@ -32,6 +33,7 @@ def test_mcp_tool_trigger_valid_creation(self):
                 "type": "mcpToolTrigger",
                 "dataType": DataType.UNDEFINED,
                 "dummyField": "dummy",
+                "metadata": '{"key": "value"}',
                 "direction": BindingDirection.IN,
             },
         )
@@ -138,6 +140,28 @@ def add_numbers(a, b):
                          '"isArray": false, '
                          '"isRequired": true}]')
 
+    def test_simple_signature_defaults_metadata(self):
+        @self.app.mcp_tool(metadata='{"key": "value"}')
+        def add_numbers(a, b):
+            return a + b
+
+        trigger = add_numbers._function._bindings[0]
+        self.assertEqual(trigger.description, "")
+        self.assertEqual(trigger.name, "context")
+        self.assertEqual(trigger.tool_name, "add_numbers")
+        self.assertEqual(trigger.metadata, '{"key": "value"}')
+        self.assertEqual(trigger.tool_properties,
+                         '[{"propertyName": "a", '
+                         '"propertyType": "string", '
+                         '"description": "", '
+                         '"isArray": false, '
+                         '"isRequired": true}, '
+                         '{"propertyName": "b", '
+                         '"propertyType": "string", '
+                         '"description": "", '
+                         '"isArray": false, '
+                         '"isRequired": true}]')
+
     def test_with_binding_argument(self):
         @self.app.mcp_tool()
         @self.app.blob_input(arg_name="file", path="", connection="Test")
@@ -415,3 +439,68 @@ def add_numbers(a) -> int:
                          '"description": "", '
                          '"isArray": false, '
                          '"isRequired": true}]')
+
+
+class TestMCPResourceTrigger(unittest.TestCase):
+    def test_mcp_resource_trigger_valid_creation(self):
+        trigger = MCPResourceTrigger(
+            name="context",
+            uri="file://readme.md",
+            resource_name="myresource",
+            title="my title",
+            description="my resource description",
+            mime_type="Text/Markdown",
+            size=1024,
+            metadata="",
+            data_type=DataType.UNDEFINED,
+            dummy_field="dummy",
+        )
+        self.assertEqual(trigger.get_binding_name(), "mcpResourceTrigger")
+        self.assertEqual(
+            trigger.get_dict_repr(),
+            {
+                "name": "context",
+                "uri": "file://readme.md",
+                "resourceName": "myresource",
+                "title": "my title",
+                "description": "my resource description",
+                "mimeType": "Text/Markdown",
+                "size": 1024,
+                "metadata": "",
+                "type": "mcpResourceTrigger",
+                "dataType": DataType.UNDEFINED,
+                "dummyField": "dummy",
+                "direction": BindingDirection.IN,
+            },
+        )
+
+    def test_mcp_resource_trigger_only_required_args_creation(self):
+        trigger = MCPResourceTrigger(
+            name="context",
+            uri="file://readme.md",
+            resource_name="myresource"
+        )
+        self.assertEqual(trigger.get_binding_name(), "mcpResourceTrigger")
+        self.assertEqual(
+            trigger.get_dict_repr(),
+            {
+                "name": "context",
+                "uri": "file://readme.md",
+                "resourceName": "myresource",
+                "type": "mcpResourceTrigger",
+                "direction": BindingDirection.IN,
+            },
+        )
+
+    def test_trigger_converter(self):
+        # Test with string data
+        datum = Datum(value='{"arguments":{}}', type='string')
+        result = MCPResourceTriggerConverter.decode(datum, trigger_metadata={})
+        self.assertEqual(result, '{"arguments":{}}')
+        self.assertIsInstance(result, str)
+
+        # Test with json data
+        datum_json = Datum(value={"arguments": {}}, type='json')
+        result_json = MCPResourceTriggerConverter.decode(datum_json, trigger_metadata={})
+        self.assertEqual(result_json, {"arguments": {}})
+        self.assertIsInstance(result_json, dict)