modelcontextprotocol/python-sdk

The official Python SDK for Model Context Protocol servers and clients

Stars: 24.3k
Forks: 4k
Open beginner issues: 49
Indexed issues: 251
Avg merge: 1d 11h
Merged PRs (30d): 30

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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A tool returning a non-finite float puts invalid JSON in the text content block Open

v1 v2

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

modelcontextprotocol/python-sdk#3385 · 1 comment · Opened Aug 25, 2026
ClientSessionGroup raises KeyError when a server exposes no tools, resources or prompts Open

v1 v2

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

modelcontextprotocol/python-sdk#3384 · 2 comments · Opened Aug 25, 2026
OAuthClientProvider auth lock is permanently poisoned when httpx closes async_auth_flow from a different task (RuntimeError: The current task is not holding this lock) Open

v1 v2

Difficulty 2/5 1-3 hours Newbie friendliness 82/100

modelcontextprotocol/python-sdk#3382 · 4 comments · Opened Aug 25, 2026
pyjwt[crypto] as an unconditional dependency blocks installation on platforms without a cryptography wheel (e.g. Windows on ARM) Open

v1 v2

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

modelcontextprotocol/python-sdk#3373 · 6 comments · Opened Aug 24, 2026
Client SSRF / protocol confusion: streamable HTTP transport follows server 3xx into internal+loopback services (follow_redirects=True, no host validation; #2106 closed but fix #2180 never merged) Open

v1 v2

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

modelcontextprotocol/python-sdk#3358 · 6 comments · Opened Aug 21, 2026
[v2] Allow MCPServer to disable subscriptions/listen Open

spec-2026-07-28 v2

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

modelcontextprotocol/python-sdk#3357 · 5 comments · 4 reactions · Opened Aug 21, 2026
Server.call_tool()'s input-validation error result discards jsonschema.ValidationError's structured fields, leaving only free-text prose Open

v1 v2

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

modelcontextprotocol/python-sdk#3351 · 1 comment · Opened Aug 21, 2026
Client treats JSON-null structuredContent as missing, skipping outputSchema validation Open

spec-2026-07-28 v2

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

modelcontextprotocol/python-sdk#3345 · 2 comments · Opened Aug 20, 2026
Prompt validation errors are logged with an unnecessary traceback Open

v1 v2

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

modelcontextprotocol/python-sdk#3342 · 2 comments · Opened Aug 20, 2026
A tool returning a non-finite float fails on the client with an error naming the tool Open

v1 v2

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

modelcontextprotocol/python-sdk#3341 · 2 comments · Opened Aug 20, 2026
Windows MCP SSH stdio transport closes after initialize when PROGRAMDATA is missing from inherited environment Open

v1 v2

Difficulty 1/5 Under an hour Newbie friendliness 25/100

modelcontextprotocol/python-sdk#3335 · 1 comment · Opened Aug 19, 2026
Add add_resource_template() to MCPServer Open

v2

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

modelcontextprotocol/python-sdk#3333 · 1 comment · Opened Aug 19, 2026
[v2] Expose the SSE max_event_size setting in Streamable HTTP clients Open

v2

modelcontextprotocol/python-sdk#3332 · 7 comments · 1 assignee · Opened Aug 18, 2026
streamable-http client: no size bound before JSONRPCMessage.model_validate_json — one large server message can OOM the client Open

v1 v2

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

modelcontextprotocol/python-sdk#3330 · 2 comments · Opened Aug 18, 2026
docs: no guidance for supporting SDK 1.x and 2.x at the same time Open

v2

Difficulty 2/5 Half a day Newbie friendliness 62/100

modelcontextprotocol/python-sdk#3309 · 10 comments · Opened Aug 14, 2026
Streamable HTTP clean EOF reconnects can exceed the request retry budget Open

bug needs confirmation P2 v1 v2

Difficulty 2/5 1-3 hours Newbie friendliness 88/100

modelcontextprotocol/python-sdk#3307 · 5 comments · Opened Aug 14, 2026
A tool returning an empty list produces a CallToolResult with zero content blocks Open

enhancement needs decision P2 v1 v2

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

modelcontextprotocol/python-sdk#3305 · 1 comment · Opened Aug 13, 2026
check_resource_allowed(): path matching skips dot-segment/percent-encoding normalization (auth-boundary bypass) Open

auth bug needs confirmation P2 v1 v2

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

modelcontextprotocol/python-sdk#3303 · 4 comments · Opened Aug 13, 2026
find_context_parameter treats a Context return annotation as a parameter Open

P3 v1 v2

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

modelcontextprotocol/python-sdk#3298 · 5 comments · Opened Aug 12, 2026
resource_url_from_server_url preserves explicit default ports Open

P3 v1 v2

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

modelcontextprotocol/python-sdk#3297 · 1 comment · Opened Aug 12, 2026
docs: clarify when Client(raise_exceptions=True) actually raises Open

P3 v1 v2

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

modelcontextprotocol/python-sdk#3287 · 1 comment · Opened Aug 11, 2026
Authentication in High Level MCPServer Open

P3 question v1 v2

Difficulty 4/5 3-5 days Newbie friendliness 38/100

modelcontextprotocol/python-sdk#3283 · 3 comments · Opened Aug 11, 2026
streamable_http (legacy mode): early response.aclose() discards a TCP connection per JSON-RPC exchange — deterministic reproduction for #2707 Open

bug P2 v1 v2

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

modelcontextprotocol/python-sdk#3281 · 1 comment · Opened Aug 11, 2026
New example: examples/servers/admission-gate — a real approve/deny ServerMiddleware demo Open

documentation P3 v2

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

modelcontextprotocol/python-sdk#3272 · 4 comments · Opened Aug 8, 2026
Mcp-Name accepts an orphan header, while Mcp-Param-* rejects it as a routing spoof Open

improves spec compliance P3 spec-2026-07-28 v2

Difficulty 3/5 1-2 days Newbie friendliness 42/100

modelcontextprotocol/python-sdk#3269 · 1 comment · Opened Aug 8, 2026
`handle_get_stream` reconnects indefinitely when the server ends the GET stream normally (`attempt = 0` defeats `MAX_RECONNECTION_ATTEMPTS`) Open

P2 v1 v2

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

modelcontextprotocol/python-sdk#3257 · 1 comment · Opened Aug 5, 2026
OAuth client can never recover from an expired DCR client secret — even though the SDK's own server issues and enforces one Open

bug P1 v1 v2

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

modelcontextprotocol/python-sdk#3256 · 1 comment · Opened Aug 5, 2026
[v2] MCPServer reports empty experimental capabilities as {} via initialize but None via server/discover Open

P2 spec-2026-07-28 v2

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

modelcontextprotocol/python-sdk#3254 · 1 comment · Opened Aug 5, 2026
OAuthClientProvider._initialize() breaks transparent refresh: missing update_token_expiry + missing oauth_metadata load Open

P1 v1 v2

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

modelcontextprotocol/python-sdk#3250 · Opened Aug 4, 2026
OAuth token refresh hits the wrong endpoint when the auth server lives under a path Open

P1 v1 v2

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

modelcontextprotocol/python-sdk#3240 · 2 comments · Opened Aug 3, 2026
Expose create_mcp_http_client and McpHttpClientFactory as public API (2.0 made them private-only) Open

P1 v2

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

modelcontextprotocol/python-sdk#3238 · 4 comments · Opened Aug 3, 2026
Parameterized Context loses request state in resource and prompt handlers Open

P1 v2

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

modelcontextprotocol/python-sdk#3235 · 2 comments · Opened Aug 1, 2026
Client-side support for the tasks extension (io.modelcontextprotocol/tasks, SEP-2663) Open

P2 spec-2026-07-28 v2

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

modelcontextprotocol/python-sdk#3226 · 3 comments · Opened Jul 30, 2026
Bug: OAuth provider holds context.lock for the whole request, so the standalone GET SSE stream stalls the first tools/call by ~15s Open

P2 v1 v2

Difficulty 4/5 3-5 days Newbie friendliness 25/100

modelcontextprotocol/python-sdk#3209 · 1 comment · Opened Jul 29, 2026
[v2] JSON-RPC error responses leave client OpenTelemetry spans UNSET Open

bug needs confirmation P2 v2

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

modelcontextprotocol/python-sdk#3174 · 9 comments · Opened Jul 26, 2026
Fix Streamable HTTP Accept header quality-factor handling Open

bug needs confirmation P3 v1 v2

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

modelcontextprotocol/python-sdk#3154 · 1 comment · Opened Jul 23, 2026
Deeply-nested-body test fails on macOS: rejected as INVALID_REQUEST (-32600) instead of PARSE_ERROR (-32700) Open

bug P3 spec-2026-07-28 v2

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

modelcontextprotocol/python-sdk#3146 · Opened Jul 22, 2026
Add `ClientSession.register_tool_schema()` for dynamic tool discovery patterns Open

enhancement needs decision P3 v1 v2

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

modelcontextprotocol/python-sdk#3145 · 3 comments · Opened Jul 22, 2026
OAuth client sends client_id in token body under client_secret_basic (strict servers reject as multiple auth methods) Open

auth bug needs confirmation P1 v1 v2

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

modelcontextprotocol/python-sdk#3138 · 6 comments · Opened Jul 21, 2026
perf: JSONRPCMessage smart union scores all four branches on every inbound message Open

enhancement needs decision P3 v1 v2

Difficulty 3/5 1-2 days Newbie friendliness 25/100

modelcontextprotocol/python-sdk#3136 · Opened Jul 19, 2026
Dispatcher mints a request id already used by a completed caller-supplied request (spec: ids MUST NOT be reused in a session) Open

bug needs confirmation P2 v2

Difficulty 3/5 1-2 days Newbie friendliness 86/100

modelcontextprotocol/python-sdk#3126 · 2 comments · Opened Jul 18, 2026
RequireAuthMiddleware omits RFC 6750 scope in WWW-Authenticate on 401/403 Open

auth bug needs confirmation P2 v1 v2

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

modelcontextprotocol/python-sdk#3103 · 2 comments · 4 reactions · Opened Jul 16, 2026
Streamable HTTP server never returns the spec-mandated 405 for GET requests it won't serve as SSE (406/400 instead) — breaks client SSE-probe fallback Open

bug needs confirmation P2 v1 v2

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

modelcontextprotocol/python-sdk#3102 · 5 comments · Opened Jul 16, 2026
Generated output schema uses Pydantic's validation shape while structured output uses its serialization shape Open

bug needs confirmation P2 v1 v2

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

modelcontextprotocol/python-sdk#3100 · 2 comments · Opened Jul 16, 2026
Field alias is published in the tool schema but forwarded as an invalid Python keyword Open

bug needs confirmation P2 v1 v2

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

modelcontextprotocol/python-sdk#3099 · 7 comments · Opened Jul 16, 2026
Heavy sync init work (e.g. local ML models) starves stdio initialize/tool calls even with threadpool offload -- Windows GIL contention Open

documentation enhancement needs decision P3 v1 v2

Difficulty 3/5 1-2 days Newbie friendliness 48/100

modelcontextprotocol/python-sdk#3089 · 3 comments · Opened Jul 12, 2026
FastMCP tool argument models silently ignore unknown/misspelled arguments (extra=ignore default) Open

enhancement needs decision P2 v1 v2

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

modelcontextprotocol/python-sdk#3067 · 1 comment · 1 reaction · Opened Jul 6, 2026
[v2] RFC 9728 PRM URLs and resource matching drop query components Open

auth bug needs confirmation P2 v1 v2

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

modelcontextprotocol/python-sdk#3065 · 2 comments · Opened Jul 6, 2026
streamable HTTP (stateful): concurrent requests with duplicate JSON-RPC ids cross-wire responses — one request receives another's payload, the other hangs Open

bug P2 v1 v2

Difficulty 4/5 3-5 days Newbie friendliness 70/100

modelcontextprotocol/python-sdk#3060 · 5 comments · 1 reaction · Opened Jul 3, 2026
FuncMetadata.pre_parse_json mis-detects str | None as non-string and corrupts JSON-looking string arguments Open

bug P2 v1 v2

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

modelcontextprotocol/python-sdk#3055 · 2 comments · Opened Jul 2, 2026

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