Why do all your MCP servers occasionally fail to grab tools?

{
  "error": "Error: Error retrieving tool list from MCP server: 'GoogleSheets'. Http status code: 405 (Method Not Allowed)"
}

I've reported this many times with no good answer. Why does this happen?

Hey Joel, could you share a few details about your setup or client you are using? It'll help us debug the Issue!

I've mentioned this before OpenAI AgentSDK, and im using your MCP server. Can you not see these error on your end, they should be logging on your hosted MCP servers

I see, looks we responded to your previous thread on Discord. Could you please check the thread and provide necessary information? Thanks!

I've provided all the information I can provide, can you not see the errors on your Hosted MCP servers? There's no logging in the platform for users.

Hey Joel, just jumping in here to help! I understand this has been frustrating for you. Let me help get this resolved. Quick check: did you try appending

/mcp

to your MCP server URL as mentioned in the [previous thread(https://discord.com/channels/1170785031560646836/1404830315427659948/1426165768353222768)? This fixes the issue in most cases. If you've tried that and it still fails, please share: 1. A minimal code snippet to reproduce this 2. OpenAI AgentSDK version (preferably package.json) About the logs: these are client-side errors, so they don't reach our servers. That's why we need the details above to troubleshoot. We really want to fix this for you and unblock you ASAP!

@openai/agents: 0.1.9

const serverUrl = `https://mcp.composio.dev/composio/server/${process.env.COMPOSIO_<INTEGRATION>_MCP_SERVER_ID}/mcp?connected_account_id=${integration.composioConnectionId}`
            tools.push(
                hostedMcpTool({
                    serverLabel: '<IntegrationName>',
                    serverUrl,
                })
            )

thanks, will load test this.

Any updates on this ? Any suggestions on mitigating ?

Hey, we were able to reproduce it (happens very rarely) & the engg team is debugging the issue. I'll keep you posted.

Thanks. It is rare in that it happens ever 1-2% of the time. But when you look at that failure rate at scale. It’s happening 10-20 times per 1000 sessions. Which isn’t much when you have a decent user base

Correct, it should never happen.

Seeing alot of this today,

{
  "error": "Error: Error retrieving tool list from MCP server: 'GoogleSheets'. Http status code: 404 (Not Found)"
}

Hey, it was a temporary issue and has been fixed now

Hey Joel, appreciate your patience here. We've investigated the

405

issue you were experiencing and wanted to share what we found. According to the [MCP specification](https://modelcontextprotocol.io/specification/2025-11-25/basic/transports#listening-for-messages-from-the-server), when a client sends an HTTP GET request to check if a server supports SSE streaming, the server should return either: - Content-Type: text/event-stream if it supports SSE, or - HTTP 405 Method Not Allowed if it doesn't The 405 response you're seeing is actually the expected behavior from our server since we don't support SSE streaming. The issue appears to be on the client side - ideally this should be handled gracefully by the client. We're investigating the 424 issue and will get back soon. Hope this is helpful, let me know if you need any clarification here.