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:
``

json

     {

       "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.