Problem in node 'AI Agent' Provider returned error using MCP Client / MCP Server Trigger

Questions
1

Hi, I am testing the new MCP Server Trigger and MCP Client nodes with a very simple workflow example. A MCP Server Trigger with 2 tools (of Airtable): getContacts and createContact:

Captura
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The main workflow (that calls MCP Server Trigger) is a simple IA Agent with a MCP client as tool. Everything seems to be working correctly with MCP nodes but the ‘IA Agent’ return the following error: Provider returned error.

I think the problem is related on the format response that MCP Client returns to ‘IA Agent’ whose structure I think ‘IA Agent’ does not know to interpret (show below):

Error
Error1007×454 33.5 KB

Output MCP Client >> IA Agent

[{ “response”: [{“type”: “text”, “text”: “[{"records":[{"id":"rec8OnAOUgj9wEL9U","createdTime":"2025-03-31T07:45:32.000Z","fields":{"nombre":"Juan Pérez","email":"[email protected]"}},{"id":"rec8sWXDfDzmpYS0h","createdTime":"2025-03-07T19:46:32.000Z","fields":{"nombre":"Álvaro García","email":"[email protected]"}}]}]”}]}]

Information about my n8n setup

  • **n8n version: 1.88.0
  • Running n8n via: web localhost:5678
  • **Operating system: Windows 10

I appreciate your help!!
Thanks in advance!!

2

Im running to exact same problem. And as same as the author mentioned, it looks like MCP returns incorrect json format. Im guessing it should be

{
 "response": "[{ 'json': 'schema_here' }]",
}

Tested this using directly connected Gmail tool to the AI Agent node and it works good

3

This is the error shown in the console:

Error MCP

4

I am having the exact same issue. Has this been resolved yet? Or is there a work around? During testing I would have to execute the step twice for it to work only to not work the third. It is working every other time.

5

The new 1.93 version seems to fix this for me.

1 Like
6

Hi Robert,

Yes, it has been solved.

Thank you!

7

I just ran mine and the same problem popped up. IT was solved for about 2 hours.

8

https://rcojinc.app.n8n.cloud/mcp/7ed7df63-7d35-467b-bb0c-c88303cc4aef/sse

9

it could be the ai agent need system prompt, also maybe on the last node of mcp trigger add a donothing node maybe it will return better.