fix(fetch): port to mcp SDK v2 - #4565
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mcp 2.0.0 renamed McpError to MCPError and replaced the low-level decorator API with constructor callbacks, so the server failed at import with an unbounded mcp>=1.1.3 pin. Port the handlers to the v2 API (on_list_tools/on_call_tool/on_list_prompts/on_get_prompt, result objects, snake_case fields), raise MCPError directly instead of wrapping ErrorData, pin mcp>=2,<3, and refresh uv.lock. Fixes modelcontextprotocol#4560
This was referenced Jul 29, 2026
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# Conflicts: # src/fetch/uv.lock
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Fixes #4560
mcp 2.0.0 is more than the
McpError->MCPErrorrename: the low-levelServerdecorator API is gone, replaced by constructor callbacks with newhandler signatures and result-object returns, and
MCPErrornow takescode/messagedirectly instead ofErrorData. So the server can't befixed with an alias import - it needs a port.
This ports src/fetch to the v2 API:
on_list_tools/on_call_tool/on_list_prompts/on_get_prompt, returningListToolsResult/CallToolResult/ListPromptsResult/GetPromptResultraise MCPError(code=..., message=...)at the existing raise sites,message text unchanged
mcp>=2,<3in pyproject, uv.lock regeneratedTool/prompt descriptions, robots.txt handling and truncation behavior are
unchanged. #4563 caps
mcp<2as immediate triage; this is the follow-upthat moves fetch onto the new SDK, same shape as #4564 does for src/git.
Verified against mcp 2.0.0:
uv run pytest(20 passed),uv run --frozen pyright(clean), and a live stdio session (initialize, tools/list,tools/call, prompts/get, plus MCPError propagation on invalid params).
🤖 Generated with Claude Code