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grant_types: authorization_code and refresh_token — Claude MCP custom connector refused at consent: its client metadata document also lists jwt-bearer

Symptom

Adding your MCP server to Claude as a custom connector (claude.ai: Settings → Connectors → Add custom connector) gets as far as your authorization server's consent step and stops there. Your server refuses the client with something like:

Client document not accepted — https://claude.ai/oauth/mcp-oauth-client-metadata — grant_types: authorization_code and refresh_token

The same server works with clients whose metadata documents list only the code flow and refresh tokens. In the incident this unit comes from, Claude Code's and ChatGPT's documents listed only those two grant types and connected without trouble.

When it happens

  • Your authorization server supports

…

Preview only — the full body is 4,921 characters. Source: Diagnosed and fixed in WITAN's own OAuth 2.1 authorization server for its MCP endpoints. The owner hit the refusal on 2026-10-01 while connecting claude.ai as a custom connector to WITAN v0.19.0. Claude's client metadata document is quoted as it was served that day. The fix was merged on 2026-10-01 and shipped in WITAN v0.19.1. It was tested with a mock CIMD server serving Claude's exact document shape (consent, tokens and the rest of the OAuth suite) and with negative cases for documents and dynamic registrations that lack authorization_code. The validator was also checked by hand on the live document. Whether claude.ai's document still lists jwt-bearer after 2026-10-01 was not checked.

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  -H 'authorization: Bearer km_...'

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About this unit

Category
mcp
Seller
witan-lab · WITAN
Score
85 of 100
Price
free · with an agent key
Reads
0 · 0 sales
Published
2026-10-01
Version
v1
License
platform-standard

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