OTel client span sets ERROR status for -32602 and other caller-error codes

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Assessment

Difficulty
2/5
Estimated time
1-3 hours
Newbie friendliness
76/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Active
Tech stack
python
Domain
observability

Research direction

Start by reading the dispatcher code that sets client-span status and error.type, then compare its behavior with the server-side classification and the MCP semantic-conventions note in docs/gen-ai/mcp.md. Reproduce with the commands in the issue if practical. Done means the five listed caller-error codes still populate rpc.response.status_code but leave status Unset and omit error.type, with tests covering that behavior.

Written by the indexing model from the issue text.

Description

bug v2

Since 2.3.0 (#3174) every JSON-RPC error response marks the client span ERROR with error.type set to the code. The OTel GenAI semantic conventions for MCP (docs/gen-ai/mcp.md, footnote on error.type) say the codes -32700, -32600, -32601, -32602 and -32002 "indicate that the caller sent a request the receiver could not serve and SHOULD NOT be considered errors"; only other codes should be. rpc.response.status_code should still carry the code.

The most common case is calling an unknown tool: the Go SDK server (and the TypeScript SDK) answer -32602, and the Python client span becomes ERROR with error.type=-32602.

Reproduction (Python 2.3.0 client against a Go SDK server):

git clone https://github.com/mkwitko/mcp-reliability && cd mcp-reliability
examples/python-sdk-streamable-http/run.sh
go run ./cmd/mcp-reliability doctor testdata/cross-python-client-go-server.jsonl

[WARN] MCP-ERR-005: span "tools/call missing" is marked failed (status=Error, error.type present=true) for a JSON-RPC code the semconv says SHOULD NOT be considered an error

Write-up: https://github.com/mkwitko/mcp-reliability/blob/v0.1.0/docs/research/python-sdk-v2-validation.md

Suggested change: in the dispatcher, when the error code is one of the five caller-error codes, set rpc.response.status_code but leave the span status Unset and skip error.type. The server side already has the equivalent classification. I can send a PR.

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