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Question

MCP OAuth Token Exchange Returning HTTP 500 Error

  • December 27, 2025
  • 2 replies
  • 21 views
C

  I'm unable to authenticate the Zapier MCP server with Claude Code. The OAuth flow completes successfully (I receive the callback with authorization code), but the token exchange fails with an HTTP 500 error.

  Error details:
  HTTP 500: Invalid OAuth error response: SyntaxError: JSON Parse error: Unrecognized token '<'

Steps I've taken:
  1. Generated a new API key from https://mcp.zapier.com
  2. Removed and re-added the MCP server with the new token
  3. Completed the OAuth authorization flow (success screen appeared)
  4. Restarted Claude Code

  The connection shows "connected" but "not authenticated" due to the 500 error during token exchange.

  Environment:
  - Client: Claude Code v2.0.76
  - MCP URL: https://mcp.zapier.com/api/mcp/mcp
  - OS: macOS

  This appears to be a server-side issue with the OAuth token endpoint. Please advise.

2 replies

drtanvisachar
Forum|alt.badge.img+1

Hello ​@corneliusschramm
It would be  helpful  if you  share a screenshot of your MCP setup and config so we  can sanity check the endpoint and auth details.

Zapier Solutions Partner-Monday Wizard
C

See screenshot attached. Here is the ID:

1f34b7e6-135f-47f0-b748-0b590ed4a013

and the MCP as a sharable link: https://mcp.zapier.com/share/5iNYY1XYcuFS6fhPwD2Frq

 

 

and here is what I have in my .claude.json

```

"zapier": {

"type": "http",

"url": "https://mcp.zapier.com/api/mcp/mcp",

"headers": {

"Authorization": "Bearer TOKEN_HERE=="

}

}

},

```

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