Figma MCP Proxy

A Go-based HTTP proxy server that enhances Model Context Protocol (MCP) tool calls by automatically adding Figma file parameters and opening Figma designs when processing tool calls.

What it does

This proxy acts as an intermediary between MCP clients and MCP servers, providing the following functionality:

1. Tool Schema Enhancement

When a client requests the list of available tools (tools/list), the proxy:

• Identifies tools that have a nodeId parameter in their input schema
• Automatically adds two additional parameters to these tools:
  • fileKey: The Figma file identifier (extracted from URLs like https://figma.com/design/1234/5678?node-id=1-2)
  • fileName: The Figma file name (extracted from the same URL format)
• Updates tool descriptions to explain how to extract these parameters from Figma URLs

2. Automatic Figma Design Opening

When processing tool calls that include both fileKey and fileName parameters, the proxy:

• Automatically opens the specified Figma design using the system's default Figma application
• Uses the figma:// URL scheme to launch directly to the design
• Supports macOS, Windows, and Linux operating systems
• Adds a 2-second delay to allow Figma to fully launch before proceeding

3. Request Logging

The proxy logs all MCP requests for debugging and monitoring purposes, including:

• HTTP method, URL path, and remote address
• Request body content (for requests under 1MB)

Architecture

The proxy uses Go's httputil.ReverseProxy to:

• Director Function: Intercepts incoming requests, parses MCP payloads, and triggers Figma design opening when appropriate
• ModifyResponse Function: Modifies tools/list responses to add the additional file parameters
• Health Endpoint: Provides a /health endpoint for monitoring proxy status

Configuration

The proxy can be configured using environment variables:

• TARGET_URL: The MCP server to proxy requests to (default: http://localhost:3845)
• PORT: The port to run the proxy server on (default: 3846)

Usage

Starting the proxy

go run main.go

Or with custom configuration:

TARGET_URL=http://localhost:3000 PORT=8080 go run main.go

Example Tool Call Flow

1. Client requests tools: POST /mcp with {"method": "tools/list"}
2. Proxy enhances response: Adds fileKey and fileName parameters to relevant tools
3. Client calls tool: POST /mcp with tool call including fileKey and fileName
4. Proxy opens Figma: Automatically launches figma://design/{fileKey}/{fileName}
5. Request forwarded: Original tool call is forwarded to the target MCP server

URL Parameter Extraction

For Figma URLs like https://figma.com/design/JqWii6wYby2bPqnaaALroQ/USER-10?node-id=1-119:

• fileKey: JqWii6wYby2bPqnaaALroQ
• fileName: USER-10

Health Check

The proxy provides a health check endpoint at /health that returns:

{
  "status": "OK",
  "targetURL": "http://localhost:3845"
}

Requirements

• Go 1.21 or later
• Figma desktop application installed on the system
• Access to the target MCP server

Cross-Platform Support

The proxy supports opening Figma designs on:

• macOS: Uses open figma://design/{fileKey}/{fileName}
• Windows: Uses PowerShell Start-Process figma://design/{fileKey}/{fileName}
• Linux: Uses xdg-open figma://design/{fileKey}/{fileName}