repository·main·Indexed 25 days ago
https://github.com/nerding-io/n8n-nodes-mcpA community node for n8n that enables workflows and AI agents to interact with Model Context Protocol (MCP) servers. It supports accessing external tools, resources, and prompts via STDIO, HTTP Streamable, and legacy SSE transports. Key operations include executing tools, retrieving prompts, and listing available resources. Version 0.1.37.
To use the MCP Client node in n8n, follow the standard n8n community nodes installation guide.
Important: If you intend to use the MCP Client node as a tool within n8n AI Agents, you MUST set the following environment variable to true:
N8N_COMMUNITY_PACKAGES_ALLOW_TOOL_USAGE=true
The listTools operation in the MCP Client node previously suffered from schema truncation because it converted the original JSON Schema from the MCP server into a Zod object and then back to JSON Schema using zodToJsonSchema. This process was lossy, removing nested structures, enums, and constraints.
To fix this, ensure the listTools operation preserves the original JSON Schema from the MCP server by passing it through directly without Zod conversion.
// Use the original JSON Schema from the MCP server directly
const aiTools = tools.map((tool: any) => ({
name: tool.name,
description: tool.description || `Execute the ${tool.name} tool`,
schema: tool.inputSchema || {type: 'object', properties: {}, additionalProperties: false},
func: async (params) => { /* ... */ }
}));To allow n8n AI Agents to use the MCP Client node as a tool, you must enable community package tool usage via environment variables.
Setup by Platform:
N8N_COMMUNITY_PACKAGES_ALLOW_TOOL_USAGE=true to your docker-compose.yml environment section.export N8N_COMMUNITY_PACKAGES_ALLOW_TOOL_USAGE=true before starting n8n..env file in the n8n directory containing N8N_COMMUNITY_PACKAGES_ALLOW_TOOL_USAGE=true.export N8N_COMMUNITY_PACKAGES_ALLOW_TOOL_USAGE=true to your ~/.zshrc or ~/.bash_profile.environment:
- N8N_COMMUNITY_PACKAGES_ALLOW_TOOL_USAGE=trueSSE transport is available for legacy compatibility but is deprecated and will not receive further updates. Use HTTP Streamable for new projects.
Credential Fields:
http://localhost:3001/sse).name:value, one per line.HTTP Streamable is the recommended transport method for new implementations. It provides better efficiency and flexibility than the deprecated SSE transport.
Credential Fields:
http://localhost:3001/stream).name:value, one per line.When using Command-line Based Transport (STDIO), you can provide environment variables to the MCP server in two ways:
NAME=VALUE format. This is ideal for individual setups and secure storage.MCP_. These will be automatically passed to the MCP servers when executed.Example Docker Configuration:
services:
n8n:
image: n8nio/n8n
environment:
- MCP_BRAVE_API_KEY=your-api-key-here
- MCP_OPENAI_API_KEY=your-openai-key-hereUse the STDIO transport to start and interact with an MCP server directly via the command line. This is useful for local servers.
Credential Fields:
npx).-y @modelcontextprotocol/server-brave-search).NAME=VALUE format.When implementing or verifying the fix for schema truncation, use a unit test to ensure that complex, nested JSON Schemas are returned identically to how they were received from the MCP server. The test should assert that the schema property in the output matches the inputSchema of the mock tool, including nested properties, formats, and required fields.
import { McpClient } from '../nodes/McpClient/McpClient.node';
// ...other imports
describe('MCP Client Tool Schema Serialization', () => {
it('should return the full, original JSON Schema for a tool', async () => {
const originalSchema = {
type: 'object',
properties: {
queries: {
type: 'array',
items: {
type: 'object',
properties: {
fg_id: { type: 'string', format: 'uuid' },
emailExact: { type: 'string', format: 'email' },
// ...more fields
},
required: ['fg_id'],
additionalProperties: false
}
}
},
required: ['queries'],
additionalProperties: false
};
// Mock the MCP server/tools response
const fakeTool = {
name: 'fg_findPersons',
description: 'Find persons based on an array of criteria.',
inputSchema: originalSchema
};
// Simulate your listTools logic here
const aiTools = [fakeTool].map(tool => ({
name: tool.name,
description: tool.description,
schema: tool.inputSchema
}));
// Assert the schema is identical
expect(aiTools[0].schema).toEqual(originalSchema);
});
});The MCP Client node supports the following operations to interact with MCP servers:
The n8n-nodes-mcp package exports a module structure required for n8n to discover and load its nodes and credential types. When integrating this package into an n8n instance, the following types are available:
mcpClient: The primary MCP Client node.mcpClientApi: Credentials for standard API access.mcpClientSseApi: Credentials for Server-Sent Events (SSE) transport.mcpClientHttpApi: Credentials for HTTP streamable transport.