Protected Resource Metadata request failed: 404 #1495
Description
Initial Checks
- I confirm that I'm using the latest version of MCP Python SDK
- I confirm that I searched for my issue in https://github.com/modelcontextprotocol/python-sdk/issues before opening this issue
Description
In python-sdk v1.18.0, the PR #1324 introduced new scopes selection and step-up authorization. but in the step 1
python-sdk/src/mcp/client/auth.py
Lines 272 to 273 in 40acbc5
It raise an error if the
oauth-protected-resource url is not found on server. this cause issue for old mcp server that does not support it yet. for example https://mcp.linear.app/sse or https://mcp.atlassian.com/v1/sse
Since we still allows discover fallback url in step 4. I suggest we should remove this exception and let the flow fall through.
Example Code
Python & MCP Python SDK
python=3.12
mcp=v1.18.0
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