Allow generic parameters to be passed onto `Context` on FastMCP tools · devilcoder/python-sdk@da54ea0 · GitHub

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Commit da54ea0

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jkawamoto

and

Kludex

authored

Allow generic parameters to be passed onto Context on FastMCP tools

Co-authored-by: Marcelo Trylesinski <marcelotryle@gmail.com>

1 parent d6e611f commit da54ea0
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2 files changed

+15-11Lines changed: 15 additions & 11 deletions

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• src/mcp/server/fastmcp/tools
  • base.py
• tests/server/fastmcp
  • test_tool_manager.py

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‎src/mcp/server/fastmcp/tools/base.py‎

Copy file name to clipboardExpand all lines: src/mcp/server/fastmcp/tools/base.py

+4-2Lines changed: 4 additions & 2 deletions

Original file line number	Diff line number	Diff line change
@@ -2,7 +2,7 @@
2	2
3	3	import inspect
4	4	from collections.abc import Callable
5		- from typing import TYPE_CHECKING, Any
	5	+ from typing import TYPE_CHECKING, Any, get_origin
6	6
7	7	from pydantic import BaseModel, Field
8	8
@@ -53,7 +53,9 @@ def from_function(
53	53	if context_kwarg is None:
54	54	sig = inspect.signature(fn)
55	55	for param_name, param in sig.parameters.items():
56		- if param.annotation is Context:
	56	+ if get_origin(param.annotation) is not None:
	57	+ continue
	58	+ if issubclass(param.annotation, Context):
57	59	context_kwarg = param_name
58	60	break
59	61

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‎tests/server/fastmcp/test_tool_manager.py‎

Copy file name to clipboardExpand all lines: tests/server/fastmcp/test_tool_manager.py

+11-9Lines changed: 11 additions & 9 deletions

Original file line number	Diff line number	Diff line change
@@ -4,8 +4,11 @@
4	4	import pytest
5	5	from pydantic import BaseModel
6	6
	7	+ from mcp.server.fastmcp import Context, FastMCP
7	8	from mcp.server.fastmcp.exceptions import ToolError
8	9	from mcp.server.fastmcp.tools import ToolManager
	10	+ from mcp.server.session import ServerSessionT
	11	+ from mcp.shared.context import LifespanContextT
9	12
10	13
11	14	class TestAddTools:
@@ -194,8 +197,6 @@ def concat_strs(vals: list[str] | str) -> str:
194	197
195	198	@pytest.mark.anyio
196	199	async def test_call_tool_with_complex_model(self):
197		- from mcp.server.fastmcp import Context
198		-
199	200	class MyShrimpTank(BaseModel):
200	201	class Shrimp(BaseModel):
201	202	name: str
@@ -223,8 +224,6 @@ def name_shrimp(tank: MyShrimpTank, ctx: Context) -> list[str]:
223	224	class TestToolSchema:
224	225	@pytest.mark.anyio
225	226	async def test_context_arg_excluded_from_schema(self):
226		- from mcp.server.fastmcp import Context
227		-
228	227	def something(a: int, ctx: Context) -> int:
229	228	return a
230	229
@@ -241,7 +240,6 @@ class TestContextHandling:
241	240	def test_context_parameter_detection(self):
242	241	"""Test that context parameters are properly detected in
243	242	Tool.from_function()."""
244		- from mcp.server.fastmcp import Context
245	243
246	244	def tool_with_context(x: int, ctx: Context) -> str:
247	245	return str(x)
@@ -256,10 +254,17 @@ def tool_without_context(x: int) -> str:
256	254	tool = manager.add_tool(tool_without_context)
257	255	assert tool.context_kwarg is None
258	256
	257	+ def tool_with_parametrized_context(
	258	+ x: int, ctx: Context[ServerSessionT, LifespanContextT]
	259	+ ) -> str:
	260	+ return str(x)
	261	+
	262	+ tool = manager.add_tool(tool_with_parametrized_context)
	263	+ assert tool.context_kwarg == "ctx"
	264	+
259	265	@pytest.mark.anyio
260	266	async def test_context_injection(self):
261	267	"""Test that context is properly injected during tool execution."""
262		- from mcp.server.fastmcp import Context, FastMCP
263	268
264	269	def tool_with_context(x: int, ctx: Context) -> str:
265	270	assert isinstance(ctx, Context)
@@ -276,7 +281,6 @@ def tool_with_context(x: int, ctx: Context) -> str:
276	281	@pytest.mark.anyio
277	282	async def test_context_injection_async(self):
278	283	"""Test that context is properly injected in async tools."""
279		- from mcp.server.fastmcp import Context, FastMCP
280	284
281	285	async def async_tool(x: int, ctx: Context) -> str:
282	286	assert isinstance(ctx, Context)
@@ -293,7 +297,6 @@ async def async_tool(x: int, ctx: Context) -> str:
293	297	@pytest.mark.anyio
294	298	async def test_context_optional(self):
295	299	"""Test that context is optional when calling tools."""
296		- from mcp.server.fastmcp import Context
297	300
298	301	def tool_with_context(x: int, ctx: Context | None = None) -> str:
299	302	return str(x)
@@ -307,7 +310,6 @@ def tool_with_context(x: int, ctx: Context | None = None) -> str:
307	310	@pytest.mark.anyio
308	311	async def test_context_error_handling(self):
309	312	"""Test error handling when context injection fails."""
310		- from mcp.server.fastmcp import Context, FastMCP
311	313
312	314	def tool_with_context(x: int, ctx: Context) -> str:
313	315	raise ValueError("Test error")

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