I am having this exact same issue myself.
When checking the devtools, I am getting 424 (Failed Dependency) errors in the list_actions:
Giving back less tools also helped! But I need the tools I had before, so it’s not a solution unfortunately
I know it is not the best solution but it looks like the only possible way as of now to use MCP tools. Let’s wait openAI and see if they are going to fix the issue.
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It’s something related to UI builder because when I export to python code everything works, even with the HostedMCPTool it is using instead of direct mcp class like MCPServerStreamableHttp.
I think they are caching some stuff on connections, my current solution is to expose the MCP servers on different endpoints and use them as new tools to agents, if I leave 1-2 days the current URL things start to not work anymore from UI.
I know it’s not a real solution, but rotating endpoints for the same mcp server is my only solution to invalidate that cache or whatever it is that stops working.
For me it’s a working workaround since I’m creating the workflow to access only local mcp servers for dev and afterwards I’m exporting them using Python code and deploy the code to dev environment where I’m replacing automatically on run time all mcp endpoints and tokens.
I’ll just leave this here…
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I have the same issues. Agent builder does connects to my local MCP server but the tools are not loading. I have tested my MCP server through MCP inspector and it working fine. Seems like the issues is not resolved yet.
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Same thing here. I have a simple n8n MCP with a single tool. This works fine on insomnia, it can detect the tool and run perfectly fine. On Agent Builder, it’s impossible to operate: Workflow failed: 400: Client error ‘400 Bad Request’ for url.
I tried to rotate the URI as suggested above, with no success.