Merge branch 'main' into fix-fastmcp-integration-tests

Author: spacelord16

README.md

@@ -1327,13 +1327,13 @@ The MCP protocol defines three core primitives that servers can implement:
 
 MCP servers declare capabilities during initialization:
 
-| Capability  | Feature Flag                 | Description                        |
-|-------------|------------------------------|------------------------------------|
-| `prompts`   | `listChanged`                | Prompt template management         |
-| `resources` | `subscribe`<br/>`listChanged`| Resource exposure and updates      |
-| `tools`     | `listChanged`                | Tool discovery and execution       |
-| `logging`   | -                            | Server logging configuration       |
-| `completion`| -                            | Argument completion suggestions    |
+| Capability   | Feature Flag                 | Description                        |
+|--------------|------------------------------|------------------------------------|
+| `prompts`    | `listChanged`                | Prompt template management         |
+| `resources`  | `subscribe`<br/>`listChanged`| Resource exposure and updates      |
+| `tools`      | `listChanged`                | Tool discovery and execution       |
+| `logging`    | -                            | Server logging configuration       |
+| `completions`| -                            | Argument completion suggestions    |
 
 ## Documentation
 

src/mcp/server/fastmcp/utilities/func_metadata.py

@@ -111,7 +111,7 @@ def convert_result(self, result: Any) -> Any:
 
             assert self.output_model is not None, "Output model must be set if output schema is defined"
             validated = self.output_model.model_validate(result)
-            structured_content = validated.model_dump(mode="json")
+            structured_content = validated.model_dump(mode="json", by_alias=True)
 
             return (unstructured_content, structured_content)
 

src/mcp/server/lowlevel/server.py

@@ -190,6 +190,7 @@ def get_capabilities(
         resources_capability = None
         tools_capability = None
         logging_capability = None
+        completions_capability = None
 
         # Set prompt capabilities if handler exists
         if types.ListPromptsRequest in self.request_handlers:
@@ -209,12 +210,17 @@ def get_capabilities(
         if types.SetLevelRequest in self.request_handlers:
             logging_capability = types.LoggingCapability()
 
+        # Set completions capabilities if handler exists
+        if types.CompleteRequest in self.request_handlers:
+            completions_capability = types.CompletionsCapability()
+
         return types.ServerCapabilities(
             prompts=prompts_capability,
             resources=resources_capability,
             tools=tools_capability,
             logging=logging_capability,
             experimental=experimental_capabilities,
+            completions=completions_capability,
         )
 
     @property

src/mcp/types.py

@@ -286,6 +286,12 @@ class LoggingCapability(BaseModel):
     model_config = ConfigDict(extra="allow")
 
 
+class CompletionsCapability(BaseModel):
+    """Capability for completions operations."""
+
+    model_config = ConfigDict(extra="allow")
+
+
 class ServerCapabilities(BaseModel):
     """Capabilities that a server may support."""
 
@@ -299,6 +305,8 @@ class ServerCapabilities(BaseModel):
     """Present if the server offers any resources to read."""
     tools: ToolsCapability | None = None
     """Present if the server offers any tools to call."""
+    completions: CompletionsCapability | None = None
+    """Present if the server offers autocompletion suggestions for prompts and resources."""
     model_config = ConfigDict(extra="allow")
 
 

tests/server/fastmcp/test_func_metadata.py

@@ -839,3 +839,48 @@ def func_returning_namedtuple() -> Point:
         func_metadata(func_returning_namedtuple, structured_output=True)
     assert "is not serializable for structured output" in str(exc_info.value)
     assert "Point" in str(exc_info.value)
+
+
+def test_structured_output_aliases():
+    """Test that field aliases are consistent between schema and output"""
+
+    class ModelWithAliases(BaseModel):
+        field_first: str | None = Field(default=None, alias="first", description="The first field.")
+        field_second: str | None = Field(default=None, alias="second", description="The second field.")
+
+    def func_with_aliases() -> ModelWithAliases:
+        # When aliases are defined, we must use the aliased names to set values
+        return ModelWithAliases(**{"first": "hello", "second": "world"})
+
+    meta = func_metadata(func_with_aliases)
+
+    # Check that schema uses aliases
+    assert meta.output_schema is not None
+    assert "first" in meta.output_schema["properties"]
+    assert "second" in meta.output_schema["properties"]
+    assert "field_first" not in meta.output_schema["properties"]
+    assert "field_second" not in meta.output_schema["properties"]
+
+    # Check that the actual output uses aliases too
+    result = ModelWithAliases(**{"first": "hello", "second": "world"})
+    unstructured_content, structured_content = meta.convert_result(result)
+
+    # The structured content should use aliases to match the schema
+    assert "first" in structured_content
+    assert "second" in structured_content
+    assert "field_first" not in structured_content
+    assert "field_second" not in structured_content
+    assert structured_content["first"] == "hello"
+    assert structured_content["second"] == "world"
+
+    # Also test the case where we have a model with defaults to ensure aliases work in all cases
+    result_with_defaults = ModelWithAliases()  # Uses default None values
+    unstructured_content_defaults, structured_content_defaults = meta.convert_result(result_with_defaults)
+
+    # Even with defaults, should use aliases in output
+    assert "first" in structured_content_defaults
+    assert "second" in structured_content_defaults
+    assert "field_first" not in structured_content_defaults
+    assert "field_second" not in structured_content_defaults
+    assert structured_content_defaults["first"] is None
+    assert structured_content_defaults["second"] is None

tests/server/test_session.py

@@ -11,8 +11,13 @@
 from mcp.shared.session import RequestResponder
 from mcp.types import (
     ClientNotification,
+    Completion,
+    CompletionArgument,
+    CompletionsCapability,
     InitializedNotification,
+    PromptReference,
     PromptsCapability,
+    ResourceReference,
     ResourcesCapability,
     ServerCapabilities,
 )
@@ -80,6 +85,7 @@ async def test_server_capabilities():
     caps = server.get_capabilities(notification_options, experimental_capabilities)
     assert caps.prompts is None
     assert caps.resources is None
+    assert caps.completions is None
 
     # Add a prompts handler
     @server.list_prompts()
@@ -89,6 +95,7 @@ async def list_prompts():
     caps = server.get_capabilities(notification_options, experimental_capabilities)
     assert caps.prompts == PromptsCapability(listChanged=False)
     assert caps.resources is None
+    assert caps.completions is None
 
     # Add a resources handler
     @server.list_resources()
@@ -98,6 +105,19 @@ async def list_resources():
     caps = server.get_capabilities(notification_options, experimental_capabilities)
     assert caps.prompts == PromptsCapability(listChanged=False)
     assert caps.resources == ResourcesCapability(subscribe=False, listChanged=False)
+    assert caps.completions is None
+
+    # Add a complete handler
+    @server.completion()
+    async def complete(ref: PromptReference | ResourceReference, argument: CompletionArgument):
+        return Completion(
+            values=["completion1", "completion2"],
+        )
+
+    caps = server.get_capabilities(notification_options, experimental_capabilities)
+    assert caps.prompts == PromptsCapability(listChanged=False)
+    assert caps.resources == ResourcesCapability(subscribe=False, listChanged=False)
+    assert caps.completions == CompletionsCapability()
 
 
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