Error when attempting to connect my Remote MCP in new Agent Builder

[isaacjmeisner]

I am attempting to connect to my custom MCP server to the new new Agent Builder, but when I supply my MCP server URL and authorization token, I get an error saying “Unable to load tools for this server”

My browser console shows error:
api.openai.com/v1/dashboard/responses/mcp/list_actions:1 Failed to load resource: the server responded with a status of 424 ()
{
“error”: {
“message”: “Error retrieving tool list from MCP server: ‘http://{{server_url_here}}:4200/mcp’. Http status code: 424 (Failed Dependency)”,
“type”: “external_connector_error”,
“param”: “tools”,
“code”: “http_error”
}
}

I have confirmed I am able to successfully inspect my MCP server via the standard MCP inspector tool

What is the issue here?

[flynn.cruse1]

I am encountering the same issue; I tried a few remote tools from smithery, including just the ‘weather’ GPT5 advised me to adjust the url’s to SSE versions, no avail.
Looking forward to these bugs being fixed so the workflows are usable!

[florian_weavelyAI]

Same issue here, made sure that the MCP was correct using MCP inspector so the issue seems to come from agent builder.

[Med_Ben_Moussa]

Same issue here, MCP connector is not working in agent builder and chatGPT

[unmahida]

Same issue here, mcp inspector is able to discover tools and run tools , but AgentBuilder is not able to discover the tool on my same remote host mcp server
Was working till yesterday, OpenAI anyone looking into this ? I am hoping to do a important demo on this tonight and now the flow is broken

[Zubair_Ahmed]

i faced the same issue… i was able to connect it but even then it produces error..

[geert]

I see that the custom header I set is simply stripped from the request going to the MCP server. Definitely for OpenAI to fix!

[Licantrop0]

Same, and I found the issue. They are adding an extra double quote around the auth header:

Hope they will fix soon. FYI @sps

[sps]

Thanks for the reports. I have sent this to the OpenAI team.

[sps]

UPDATE: The team has already deployed a fix for this issue. Let me know if you are still experiencing this.

[marc22761]

@sps Thanks for the fast response and quick solution, unfortunately, it didn’t solved it yet. At least not for me.

[florian_weavelyAI]

Same here, issue is still there. Trying to connect to an MCP server using SSE and no auth.

[sps]

I recently tested it and found that it works on MCP servers, both with authentication enabled (using bearer tokens) and without any authentication. Please let me know the details if you’re having a different experience!

[florian_weavelyAI]

Are you using an MCP server that supports SSE or streamable HTTP ? You can’t specify the option in the modal so I figured that it would automatically detect which protocol is being used … but maybe that’s the issue ?

[marc22761]

@sps Your UI looks different then mine!!??

[marc22761]

https://platform.openai.com/agent-builder/edit?version=draft&workflow=

[sps]

@florian_weavelyAI
I’m using mcp-handler for the server deployed on Vercel.

It uses streamable HTTP which replaces the older HTTP + SSE.

[sps]

You’ll get to this UI from the one you shared once the MCP server is connected.

[marc22761]

Anyone being succesful yet? I’m still stuck.

[AniManage]

I’m experiencing the same 424 “Failed Dependency” error with OpenAI Agent Builder when trying to connect my MCP server. After extensive testing, I confirmed my MCP server works perfectly with direct API calls (initialize and tools/list both return valid responses), but Agent Builder’s internal processing fails with 424 errors on list_actions requests. The issue is in OpenAI’s internal validation layer (https://api.openai.com/v1/dashboard/responses/mcp/list_actions), not in my MCP server configuration or authentication. This appears to be a OpenAI Agent Builder bug affecting multiple users with working MCP servers. Hopefully they will fix it soon.

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