n8n-nodes-mcp-client

Built by 4Runr, this is a custom n8n node that connects to a self-hosted MCP Server via Server-Sent Events (SSE). It streams tool definitions to n8n AI Agents in real time, enabling flexible, dynamic automation at scale.

Features

• Listens to an sseUrl endpoint for incoming tools events.
• Emits tool definitions for use in the n8n AI Agent ecosystem.
• Allows dynamic tool selection and parameter input.
• Executes tools by POSTing to /mcp/message with the correct payload and headers.
• Logs events, handles errors, and filters events automatically.
• Optimized for 4Runr's AI automation infrastructure and MCP server systems.

Usage

1. Configure Credentials

   • Set up a credential of type 4Runr MCP Access with:
     • SSE URL (required): Your MCP server's SSE endpoint (e.g., https://mcp-server/mcp-events)
     • SSE Connection Timeout (optional): Timeout in ms (default: 60000)
     • Messages POST Endpoint (required): Your MCP server's message endpoint (e.g., https://mcp-server/mcp/message)
     • Additional Headers (optional): JSON for API keys, etc. (e.g., { "X-API-Key": "Test12345" })

2. Add the Node to Your Workflow

   • Use the "4Runr MCP Client" node as a tool source in your AI Agent configuration.
   • The node will dynamically display available tools as they arrive from the SSE stream.
   • You can select a tool and input parameters (as JSON) to execute it.

3. Tool Execution

   • When a tool is executed, the node will POST to the configured message endpoint with the payload:

     {
       "toolCall": {
         "toolName": "check_availability",
         "parameters": { ... }
       }
     }

   • The X-API-Key header (if provided) will be included in all POST requests.

4. Error Handling

   • The node provides robust error handling for SSE, JSON parsing, and HTTP errors.
   • Errors are logged and displayed in the n8n UI.

Assumptions

• Tool names are accepted as sent by the server (namespacing/aliasing is optional).
• All tool parameters and required/optional flags are respected as sent by the server.
• The node expects the MCP server to emit a tools event with a tools array in the data payload.

Advanced/Optional

• Tool name mapping/aliasing is supported via the Tool Name Mapping (Optional) property.
• Future enhancements may include caching, custom parameter UI, and more.

Maintainer

Developed and maintained by 4Runr — Montreal's AI infrastructure company transforming how businesses run with intelligent systems.