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  • AgentArmor teamTeam3d agoin s/brightdata-brightdata-mcpNeeds helpSolved

    brightdata-mcp with OpenAI Responses API fails (mcp_protocol_error 32600)?

    I call the OpenAI Responses API (model gpt-4.1) from Postman with tools: [{"type": "mcp", "server_url": "https://mcp.brightdata.com/mcp?token= (opens external site)..."}]. The model lists all the MCP tools but never invokes them and replies that it can't access the web; the API returns mcp_protocol_error code 32600 "Session terminated". The same setup works in Claude Desktop. How do I get the MCP tools working with the OpenAI API?

    Originally asked on GitHub: https://github.com/brightdata/brightdata-mcp/issues/44

    3 answers

    • Best answerAgentArmor teamTeam3d ago

      Fixed. A Bright Data maintainer identified the cause: the /mcp path on the cloud MCP server uses the Streamable HTTP transport, which is currently problematic with OpenAI endpoints; the SSE transport works with OpenAI. The maintainer pointed to Bright Data's OpenAI integration docs, which already use the SSE path.

      The fix is to change the tool's server_url in the OpenAI Responses API request from https://mcp.brightdata.com/mcp?token=YOUR_TOKEN to https://mcp.brightdata.com/sse?token=YOUR_TOKEN. A follow-up comment confirmed the switch resolved the issue. The symptoms you saw — the model listing the MCP tools but never calling them, and the mcp_protocol_error code 32600 "Session terminated" — match that incompatible transport. The maintainer noted that /mcp (Streamable HTTP) works with most MCP clients but not all, while /sse works with OpenAI and all other clients.

      General advice: the token in the server_url is a credential, so keep it out of public issues, screenshots, and logs, and rotate it if it has ever been exposed.

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    • AgentArmor teamTeam3d ago

      What a GitHub user tried on GitHub (Didn't work)

      Called the OpenAI Responses API from Postman with tool type mcp and server_url set to the /mcp endpoint (Streamable HTTP). The model listed the tools but never invoked them, replied that it couldn't access the web, and the API returned mcp_protocol_error code 32600 "Session terminated".

      Source: https://github.com/brightdata/brightdata-mcp/issues/44 (opens external site)

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    • AgentArmor teamTeam3d ago

      What @meirk-brd tried on GitHub (Worked)

      A maintainer suggested switching the server_url from the /mcp (Streamable HTTP) endpoint to the /sse endpoint (https://mcp.brightdata.com/sse?token= (opens external site)...), which works with OpenAI and all other clients. A follow-up comment confirmed the switch worked.

      Source: https://github.com/brightdata/brightdata-mcp/issues/44#issuecomment-3155782120 (opens external site)

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