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fix: correct MCPServer call_tool result type (#2816)

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Co-authored-by: Marcelo Trylesinski <marcelotryle@gmail.com>
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冯基魁 2026-06-20 22:56:16 +08:00 • committed by GitHub
commit fda4c54362
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1 changed files with 63 additions and 45 deletions
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25
src/mcp/server/mcpserver/server.py
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@ -4,9 +4,8 @@ from __future__ import annotations
import base64
import inspect
import json
import re
from collections.abc import AsyncIterator, Awaitable, Callable, Iterable, Sequence
from collections.abc import AsyncIterator, Awaitable, Callable, Iterable
from contextlib import AbstractAsyncContextManager, asynccontextmanager
from typing import Any, Generic, Literal, TypeVar, overload
@ -53,7 +52,6 @@ from mcp.types import (
CompleteRequestParams,
CompleteResult,
Completion,
ContentBlock,
GetPromptRequestParams,
GetPromptResult,
Icon,
@ -311,28 +309,11 @@ class MCPServer(Generic[LifespanResultT]):
) -> CallToolResult:
context = Context(request_context=ctx, mcp_server=self)
try:
result = await self.call_tool(params.name, params.arguments or {}, context)
return await self.call_tool(params.name, params.arguments or {}, context)
except MCPError:
raise
except Exception as e:
return CallToolResult(content=[TextContent(type="text", text=str(e))], is_error=True)
if isinstance(result, CallToolResult):
return result
if isinstance(result, tuple) and len(result) == 2:
unstructured_content, structured_content = result
return CallToolResult(
content=list(unstructured_content), # type: ignore[arg-type]
structured_content=structured_content, # type: ignore[arg-type]
)
if isinstance(result, dict): # pragma: no cover
# TODO: this code path is unreachable — convert_result never returns a raw dict.
# The call_tool return type (Sequence[ContentBlock] | dict[str, Any]) is wrong
# and needs to be cleaned up.
return CallToolResult(
content=[TextContent(type="text", text=json.dumps(result, indent=2))],
structured_content=result,
)
return CallToolResult(content=list(result))
async def _handle_list_resources(
self, ctx: ServerRequestContext[LifespanResultT], params: PaginatedRequestParams | None
@ -406,7 +387,7 @@ class MCPServer(Generic[LifespanResultT]):
async def call_tool(
self, name: str, arguments: dict[str, Any], context: Context[LifespanResultT, Any] | None = None
) -> Sequence[ContentBlock] | dict[str, Any]:
) -> CallToolResult:
"""Call a tool by name with arguments."""
if context is None:
context = Context(mcp_server=self)