modelcontextprotocol/python-sdk

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The official Python SDK for Model Context Protocol servers and clients

Stars: 24.3k
Forks: 4k
Open beginner issues: 17
Indexed issues: 241
Avg merge: 1d 1h
Merged PRs (30d): 31

Dominant language: Python
License: MIT
Last GitHub push: Sep 16, 2026
Latest indexed: Sep 20, 2026
Contributing guide: Contributing guide
Code of conduct: Code of conduct
Beginner labels: good first issue help wanted

Beginner friendly Everything

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241 open issues indexed

Deep JSON-RPC request over stdio logs a validation error and leaves the original request pending Open

bug needs confirmation P2

Difficulty 4/5 3-5 days Newbie friendliness 47/100

modelcontextprotocol/python-sdk#2751 · 1 comment · Opened Jun 1, 2026
Stateful Streamable HTTP: in-session exceptions are masked as an empty -32603; real cause only in a separate "Session crashed" log Open

bug needs confirmation P2

Difficulty 4/5 3-5 days Newbie friendliness 52/100

modelcontextprotocol/python-sdk#2741 · 2 comments · Opened May 31, 2026
streamable_http client does not send `Origin` header → rejected with 403 by spec-compliant servers (e.g. go-sdk `CrossOriginProtection`) Open

enhancement needs decision P3

Difficulty 2/5 1-3 hours Newbie friendliness 75/100

modelcontextprotocol/python-sdk#2727 · 3 comments · Opened May 30, 2026
FastMCP: streamable_http_app() silently breaks when BaseHTTPMiddleware is added Open

bug needs repro P3 potentially close

Difficulty 3/5 1-2 days Newbie friendliness 64/100

modelcontextprotocol/python-sdk#2702 · 5 comments · Opened May 27, 2026
`ClientSessionGroup` attempts to use capabilities that were not advertised Open

bug fix proposed P2 ready for work

Difficulty 2/5 1-3 hours Newbie friendliness 76/100

modelcontextprotocol/python-sdk#2689 · 3 comments · Opened May 26, 2026
`OAuthClientInformationFull.redirect_uris`: pydantic strict-type-equality breaks `AnyUrl(x) != AnyHttpUrl(x)` round-trip Open

auth bug fix proposed P2 ready for work

Difficulty 3/5 1-2 days Newbie friendliness 72/100

modelcontextprotocol/python-sdk#2687 · 3 comments · Opened May 26, 2026
FastMCP/stdio: in-flight tool responses dropped on stdin EOF when input is bash-redirected from a file Open

bug P2 ready for work

Difficulty 4/5 3-5 days Newbie friendliness 55/100

modelcontextprotocol/python-sdk#2678 · 8 comments · Opened May 25, 2026
ClientSession receive loop swallows callback exceptions, replying "Invalid request parameters" to the server instead of propagating to the call_tool awaiter Open

enhancement needs decision P3

Difficulty 3/5 1-2 days Newbie friendliness 68/100

modelcontextprotocol/python-sdk#2673 · 4 comments · Opened May 24, 2026
FastMCP.run(transport="stdio") produces noisy traceback on KeyboardInterrupt instead of clean exit Open

bug fix proposed P3 ready for work

Difficulty 3/5 1-2 days Newbie friendliness 64/100

modelcontextprotocol/python-sdk#2663 · 3 comments · Opened May 22, 2026
Streamable HTTP server silently drops in-flight request when client reuses a JSON-RPC id Open

bug fix proposed P2 ready for work

Difficulty 3/5 1-2 days Newbie friendliness 68/100

modelcontextprotocol/python-sdk#2655 · 3 comments · Opened May 21, 2026
mcp.server.fastmcp.FastMCP HTTP transport deadlocks after ~5 sequential client sessions on Windows (companion to PrefectHQ/fastmcp#4192) Open

bug needs repro

Difficulty 4/5 3-5 days Newbie friendliness 42/100

modelcontextprotocol/python-sdk#2653 · 3 comments · Opened May 21, 2026
DCR registration accepts redirect_uris with non-HTTPS / non-loopback / fragmented schemes Open

auth bug fix proposed P2 ready for work

Difficulty 3/5 1-2 days Newbie friendliness 67/100

modelcontextprotocol/python-sdk#2629 · 1 comment · Opened May 18, 2026
Add option to skip output validation for mcp client Open

enhancement needs decision P3

Difficulty 3/5 1-2 days Newbie friendliness 65/100

modelcontextprotocol/python-sdk#2626 · 3 comments · Opened May 17, 2026
RequestResponder.__exit__ leaks CancelledError on cancelled request, killing the stdio receive loop Open

bug needs confirmation P2 potentially close

Difficulty 3/5 1-2 days Newbie friendliness 68/100

modelcontextprotocol/python-sdk#2610 · 3 comments · Opened May 15, 2026
Duplicate `initialize` with changed parameters can overwrite `ServerSession.client_params` Open

bug fix proposed P2 ready for work

Difficulty 4/5 3-5 days Newbie friendliness 48/100

modelcontextprotocol/python-sdk#2605 · 4 comments · Opened May 15, 2026
`ClientConfig` has inconsistent naming: `message_handler` should be `message_callback` Open

enhancement needs decision P3 v2

Difficulty 3/5 1-2 days Newbie friendliness 73/100

modelcontextprotocol/python-sdk#2588 · Opened May 13, 2026
Expose `schema_generator` on `FastMCP` for tool params schema generation Open

enhancement needs decision P3

Difficulty 3/5 1-2 days Newbie friendliness 55/100

modelcontextprotocol/python-sdk#2582 · Opened May 13, 2026
OAuth token refresh sends RFC 8707 resource parameter that Entra ID v2.0 rejects (AADSTS9010010) Open

auth bug fix proposed P2 ready for work

Difficulty 4/5 3-5 days Newbie friendliness 55/100

modelcontextprotocol/python-sdk#2578 · 6 comments · Opened May 12, 2026
raise without from discards exception chain in 12 remaining sites Open

bug P3

Difficulty 3/5 1-2 days Newbie friendliness 74/100

modelcontextprotocol/python-sdk#2564 · 3 comments · Opened May 8, 2026
Add `list_all_*` helpers to drain pagination Open

enhancement P3 v2

Difficulty 3/5 1-2 days Newbie friendliness 52/100

modelcontextprotocol/python-sdk#2556 · 3 comments · Opened May 8, 2026
Split the core from the server and client implementations Open

enhancement needs decision P3 v2

Difficulty 5/5 Over a week Newbie friendliness 35/100

modelcontextprotocol/python-sdk#2486 · 4 comments · Opened Apr 21, 2026
Return 405 on GET when stateless_http=True Open

bug P2

Difficulty 2/5 1-3 hours Newbie friendliness 68/100

modelcontextprotocol/python-sdk#2474 · 4 comments · 2 reactions · Opened Apr 19, 2026
MCPServer unconditionally declares `prompts`, `resources`, `tools` capabilities on `initialize` Open

bug P2

Difficulty 4/5 3-5 days Newbie friendliness 45/100

modelcontextprotocol/python-sdk#2473 · Opened Apr 19, 2026
stdio_client crashes on malformed UTF-8 from child stdout instead of surfacing parse error Open

bug fix proposed P2 ready for work

Difficulty 3/5 1-2 days Newbie friendliness 78/100

modelcontextprotocol/python-sdk#2454 · 3 comments · Opened Apr 16, 2026
Windows: TextIOWrapper in stdio_server() emits CRLF instead of LF, corrupting newline-delimited JSON messages Open

bug fix proposed P2 ready for work

Difficulty 1/5 Under an hour Newbie friendliness 88/100

modelcontextprotocol/python-sdk#2433 · 9 comments · Opened Apr 13, 2026
Initialize call hangs forever if MCP server does not return a `Content-Type: text/plain` Open

bug fix proposed P2 ready for work

Difficulty 3/5 1-2 days Newbie friendliness 58/100

modelcontextprotocol/python-sdk#2432 · 3 comments · Opened Apr 13, 2026
McpError is not pickle-safe and fails to unpickle Open

bug fix proposed P2 ready for work

Difficulty 2/5 1-3 hours Newbie friendliness 74/100

modelcontextprotocol/python-sdk#2431 · 9 comments · Opened Apr 13, 2026
[v1.x] Server-side outputSchema validation blocks tool error reporting (isError: true) Open

bug fix proposed P2 ready for work

Difficulty 3/5 1-2 days Newbie friendliness 70/100

modelcontextprotocol/python-sdk#2429 · 2 comments · Opened Apr 13, 2026
Specific ToolNotFoundError for easier handling than ToolError in multi-tenant environments Open

enhancement needs decision P3

Difficulty 3/5 1-2 days Newbie friendliness 50/100

modelcontextprotocol/python-sdk#2422 · 4 comments · Opened Apr 10, 2026
Bug: AssertionError: Request already responded to — cancellation race in v1.27.0 Open

bug fix proposed P2 ready for work

Difficulty 4/5 3-5 days Newbie friendliness 68/100

modelcontextprotocol/python-sdk#2416 · 14 comments · Opened Apr 9, 2026
StreamableHTTP client: _handle_reconnection resets attempt counter to 0, causing infinite retry loop Open

bug P2

Difficulty 2/5 1-3 hours Newbie friendliness 78/100

modelcontextprotocol/python-sdk#2393 · 2 comments · Opened Apr 5, 2026
Inline $ref in tool inputSchema for LLM consumption (parity with typescript-sdk) Open

enhancement needs decision P2

Difficulty 3/5 1-2 days Newbie friendliness 68/100

modelcontextprotocol/python-sdk#2384 · 2 comments · Opened Apr 2, 2026
ClientSession: add public API for updating callbacks after initialization Open

enhancement needs decision P3

Difficulty 2/5 1-3 hours Newbie friendliness 70/100

modelcontextprotocol/python-sdk#2379 · 4 comments · Opened Mar 30, 2026
Image/ImageContent serialization fails in stateless HTTP mode Open

bug needs confirmation P2

Difficulty 3/5 1-2 days Newbie friendliness 55/100

modelcontextprotocol/python-sdk#2376 · 3 comments · 5 reactions · Opened Mar 29, 2026
Design: future of `dependencies` parameter on MCPServer Open

enhancement needs decision P2 v2

Difficulty 5/5 Over a week Newbie friendliness 35/100

modelcontextprotocol/python-sdk#2354 · 2 comments · 4 reactions · Opened Mar 26, 2026
Add remove_prompt() and remove_resource() for parity with remove_tool() Open

enhancement needs decision P3

Difficulty 3/5 1-2 days Newbie friendliness 72/100

modelcontextprotocol/python-sdk#2331 · 4 comments · Opened Mar 22, 2026
Improve log clarity for "Terminating session: None" in stateless mode Open

enhancement P3

Difficulty 2/5 1-3 hours Newbie friendliness 45/100

modelcontextprotocol/python-sdk#2329 · 1 comment · Opened Mar 22, 2026
Don't override client_metadata.scopes if they are already set Open

auth enhancement needs decision P2

Difficulty 2/5 1-3 hours Newbie friendliness 68/100

modelcontextprotocol/python-sdk#2317 · 5 comments · Opened Mar 20, 2026
Mark SSE transport as deprecated Open

improves sdk consistency improves spec compliance P3 v2

Difficulty 3/5 1-2 days Newbie friendliness 68/100

modelcontextprotocol/python-sdk#2278 · 1 comment · Opened Mar 11, 2026
pywin32 installation fails on Windows — hard dep only needed for client stdio, but pulled in for all users via eager import in __init__.py Open

enhancement needs decision P2

Difficulty 3/5 1-2 days Newbie friendliness 76/100

modelcontextprotocol/python-sdk#2233 · 3 comments · Opened Mar 6, 2026
Bug: validate_scope rejects client scopes when required scopes in None Open

auth bug P2 ready for work

Difficulty 2/5 1-3 hours Newbie friendliness 64/100

modelcontextprotocol/python-sdk#2216 · 5 comments · Opened Mar 5, 2026
Type the MCPServer handler pipeline: tool/resource/prompt return types Open

enhancement v2

Difficulty 4/5 3-5 days Newbie friendliness 48/100

modelcontextprotocol/python-sdk#2202 · Opened Mar 2, 2026
MCPServer handlers should raise exceptions, not return error objects Open

enhancement v2

Difficulty 5/5 Over a week Newbie friendliness 35/100

modelcontextprotocol/python-sdk#2153 · Opened Feb 27, 2026
Active Streamable HTTP sessions are not terminated during shutdown Open

bug P2 ready for work

Difficulty 4/5 3-5 days Newbie friendliness 48/100

modelcontextprotocol/python-sdk#2150 · 3 comments · Opened Feb 26, 2026
Add wildcard pattern support for `allowed_hosts` in transport security Open

enhancement needs confirmation

modelcontextprotocol/python-sdk#2141 · 1 comment · 1 assignee · Opened Feb 25, 2026
Allow `OAuthClientProvider` to accept a pre-configured auth server URL Open

auth enhancement needs confirmation

modelcontextprotocol/python-sdk#2121 · 1 assignee · Opened Feb 21, 2026
Support MCP client session resumption (sessionId reuse) in Python SDK Open

enhancement P2 v2

Difficulty 5/5 Over a week Newbie friendliness 35/100

modelcontextprotocol/python-sdk#2116 · 2 comments · 1 reaction · Opened Feb 20, 2026
ExceptionGroup wrapping obscures real errors from task groups Open

bug P1 v2

Difficulty 4/5 3-5 days Newbie friendliness 48/100

modelcontextprotocol/python-sdk#2114 · 3 comments · 2 reactions · Opened Feb 19, 2026
HTTP transport swallows non-2xx status codes causing client to hang Open

bug P1 v2

Difficulty 4/5 3-5 days Newbie friendliness 48/100

modelcontextprotocol/python-sdk#2110 · 7 comments · 2 reactions · Opened Feb 19, 2026
Expose session, auth, and transport information on handler Context Open

enhancement P1 v2

Difficulty 5/5 Over a week Newbie friendliness 35/100

modelcontextprotocol/python-sdk#2098 · 1 comment · Opened Feb 19, 2026

modelcontextprotocol/python-sdk

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