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fix: support MCP Python SDK v2 in the SDK MCP bridge #1157

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fix: support MCP Python SDK v2 in the SDK MCP bridge #1157

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2 changes: 1 addition & 1 deletion pyproject.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -28,7 +28,7 @@ dependencies = [
"anyio>=4.0.0",
"sniffio>=1.0.0",
"typing_extensions>=4.0.0; python_version<'3.11'",
"mcp>=1.23.0,<2.0.0",
"mcp>=1.23.0,<3.0.0",
]

[project.optional-dependencies]
Expand Down
55 changes: 45 additions & 10 deletions src/claude_agent_sdk/__init__.py
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Original file line number Diff line number Diff line change
Expand Up @@ -384,9 +384,12 @@ def create_sdk_mcp_server(
from mcp.server import Server
from mcp.types import (
AudioContent,
CallToolRequestParams,
CallToolResult,
EmbeddedResource,
ImageContent,
ListToolsResult,
PaginatedRequestParams,
ResourceLink,
TextContent,
Tool,
Expand Down Expand Up @@ -446,14 +449,10 @@ def _build_meta(tool_def: "SdkMcpTool[Any]") -> dict[str, Any] | None:
for tool_def in tools
]

# Register list_tools handler to expose available tools
@server.list_tools() # type: ignore[no-untyped-call,untyped-decorator]
async def list_tools() -> list[Tool]:
"""Return the list of available tools."""
return cached_tool_list

# Register call_tool handler to execute tools
@server.call_tool() # type: ignore[untyped-decorator]
async def call_tool(name: str, arguments: dict[str, Any]) -> Any:
"""Execute a tool by name with given arguments."""
if name not in tool_map:
Expand All @@ -477,11 +476,15 @@ async def call_tool(name: str, arguments: dict[str, Any]) -> Any:
if item_type == "text":
content.append(TextContent(type="text", text=item["text"]))
elif item_type == "image":
# Built from the wire names: MCP SDK v2 renamed the
# field to mime_type and kept mimeType as its alias.
content.append(
ImageContent(
type="image",
data=item["data"],
mimeType=item["mimeType"],
ImageContent.model_validate(
{
"type": "image",
"data": item["data"],
"mimeType": item["mimeType"],
}
)
)
elif item_type == "resource_link":
Expand Down Expand Up @@ -517,8 +520,40 @@ async def call_tool(name: str, arguments: dict[str, Any]) -> Any:
item_type,
)

return CallToolResult(
content=content, isError=result.get("is_error", False)
return CallToolResult.model_validate(
{"content": content, "isError": result.get("is_error", False)}
)

# Register the handlers. MCP SDK v1 uses decorators; v2 registers by
# method name and passes a request context plus parsed params. Only one
# of the two APIs exists on any given install, so go through Any.
registry: Any = server
if hasattr(server, "list_tools"):
registry.list_tools()(list_tools)
registry.call_tool()(call_tool)
else:

async def on_list_tools(ctx: Any, params: Any) -> Any:
return ListToolsResult(tools=await list_tools())

async def on_call_tool(ctx: Any, params: Any) -> Any:
# v1's call_tool decorator reports handler exceptions as an
# error result rather than a protocol error; keep that here.
try:
return await call_tool(params.name, params.arguments or {})
except Exception as e:
return CallToolResult.model_validate(
{
"content": [TextContent(type="text", text=str(e))],
"isError": True,
}
)

registry.add_request_handler(
"tools/list", PaginatedRequestParams, on_list_tools
)
registry.add_request_handler(
"tools/call", CallToolRequestParams, on_call_tool
)

# Return SDK server configuration
Expand Down
70 changes: 36 additions & 34 deletions src/claude_agent_sdk/_internal/query.py
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Original file line number Diff line number Diff line change
Expand Up @@ -56,6 +56,23 @@
DEFERRING_TASK_TYPES = frozenset({"local_agent", "local_workflow"})


async def _call_sdk_mcp_handler(server: Any, request: Any) -> Any:
"""Invoke an SDK MCP server's handler for a request, or None if unhandled.

MCP SDK v1 keys handlers by request type and wraps the result in a
ServerResult; v2 keys them by method name and returns the result directly.
"""
handlers = getattr(server, "request_handlers", None)
if handlers is not None:
handler = handlers.get(type(request))
return (await handler(request)).root if handler else None
entry = server.get_request_handler(request.method)
if entry is None:
return None
# Handlers registered by create_sdk_mcp_server() ignore the context.
return await entry.handler(None, request.params)


def _convert_hook_output_for_cli(hook_output: dict[str, Any]) -> dict[str, Any]:
"""Convert Python-safe field names to CLI-expected field names.

Expand Down Expand Up @@ -646,30 +663,15 @@ async def _handle_sdk_mcp_request(

elif method == "tools/list":
request = ListToolsRequest(method=method)
handler = server.request_handlers.get(ListToolsRequest)
if handler:
result = await handler(request)
# Convert MCP result to JSONRPC response
tools_data = []
for tool in result.root.tools: # type: ignore[union-attr]
tool_data: dict[str, Any] = {
"name": tool.name,
"description": tool.description,
"inputSchema": (
tool.inputSchema.model_dump()
if hasattr(tool.inputSchema, "model_dump")
else tool.inputSchema
)
if tool.inputSchema
else {},
}
if tool.annotations:
tool_data["annotations"] = tool.annotations.model_dump(
exclude_none=True
)
if tool.meta:
tool_data["_meta"] = tool.meta
tools_data.append(tool_data)
result = await _call_sdk_mcp_handler(server, request)
if result is not None:
# Convert MCP result to JSONRPC response. Dumping by alias
# yields the wire names (inputSchema, _meta, ...) on both
# MCP SDK v1 and v2, which renamed the fields to snake_case.
tools_data = [
tool.model_dump(by_alias=True, exclude_none=True, mode="json")
for tool in result.tools
]
return {
"jsonrpc": "2.0",
"id": message.get("id"),
Expand All @@ -683,24 +685,21 @@ async def _handle_sdk_mcp_request(
name=params.get("name"), arguments=params.get("arguments", {})
),
)
handler = server.request_handlers.get(CallToolRequest)
if handler:
result = await handler(call_request)
result = await _call_sdk_mcp_handler(server, call_request)
if result is not None:
# Convert MCP result to JSONRPC response
content = []
for item in result.root.content: # type: ignore[union-attr]
for item in result.content:
item_type = getattr(item, "type", None)
if item_type == "text":
content.append(
{"type": "text", "text": getattr(item, "text", "")}
)
elif item_type == "image":
content.append(
{
"type": "image",
"data": getattr(item, "data", ""),
"mimeType": getattr(item, "mimeType", ""),
}
item.model_dump(
by_alias=True, exclude_none=True, mode="json"
)
)
elif item_type == "resource_link":
parts = []
Expand Down Expand Up @@ -736,7 +735,10 @@ async def _handle_sdk_mcp_request(
)

response_data = {"content": content}
if hasattr(result.root, "isError") and result.root.isError:
# MCP SDK v2 renamed isError to is_error.
if getattr(result, "isError", None) or getattr(
result, "is_error", None
):
response_data["isError"] = True # type: ignore[assignment]

return {
Expand Down
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