Figma MCPA local companion for Figma documents

Overview ​

Figma MCP is a local companion for Figma documents with the Figma Bridge plugin open. An MCP client starts the .NET process and exchanges protocol messages with it over STDIO.

sequenceDiagram
    participant Client as MCP client
    participant Companion as Companion
    participant Registry as Connection registry
    participant Plugin as Bridge plugin
    participant Figma as Figma API

    Client->>Companion: Start the child process and establish MCP over STDIO
    Plugin->>Companion: Open the loopback WebSocket using figma-mcp-bridge.v2
    Companion->>Registry: Validate the hello message and register connection_id
    Companion-->>Plugin: Confirm registration with hello_ack
    Client->>Companion: Call a document tool with the selected connection_id
    Companion->>Registry: Resolve the live connection and allocate request_id
    Registry-->>Companion: Return the active plugin connection
    Companion->>Plugin: Send a bounded MessagePack bridge request
    Plugin->>Figma: Read or mutate the active Figma document
    Figma-->>Plugin: Return the operation result
    Plugin-->>Companion: Send the MessagePack response with request_id
    Companion-->>Client: Return the matched MCP result over stdout

The companion has two transport roles:

• STDIO serves MCP. Protocol messages use stdin and stdout; diagnostics use stderr.
• The loopback WebSocket endpoint at /bridge serves the Figma Bridge plugin.

The server, plugin, and bridge use explicit typed contracts. Document-specific MCP tools receive a live connection_id, and bridge operations use bounded payloads, a 30-second deadline, and idempotent mutation keys where applicable.

Starting the companion ​

Install the cross-platform .NET tool from NuGet.org:

dotnet tool install --global FigmaMCP

The MCP client starts the tool as a child process:

{
  "mcpServers": {
    "figma": {
      "command": "figma-mcp-server"
    }
  }
}

Alternatively, download a self-contained win-x64, linux-x64, or osx-arm64 archive from the matching GitHub Release. A Windows client configuration can then look like this:

{
  "mcpServers": {
    "figma": {
      "command": "C:\\path\\to\\FigmaMCP.exe"
    }
  }
}

The process listens on 127.0.0.1:3846/bridge for the plugin by default. If no --port is supplied and 3846 is occupied, it detects that before Kestrel starts, tries subsequent ports through 65535, and reports the selected fallback on stderr. Pass --port <1-65535> to use one specific bridge port; an explicit port is never changed. Set the Bridge plugin to the port the server selected. The bridge is loopback-only and must not bind to an external interface.

Documentation map ​

• Architecture explains transports, lifecycle, state, and security boundaries.
• Development describes the repository layout, build commands, and local checks.
• Tool reference defines the MCP tool contract.
• Plugin API coverage records supported and deferred Figma API areas.