MCP Server Configuration Manual

Introduction

The MCP Flake provides declarative configuration for Model Control Protocol servers and clients.

Features

Cross-platform support (NixOS, Darwin, home-manager)
Pure Nix expressions for maximum compatibility
Declarative configuration with support for secret management
Support for various MCP servers including filesystem and GitHub servers
Automatic generation of client configurations at appropriate OS-specific paths

Configuration Options

Base Options

`services.mcpServers.enable`

Whether to enable MCP servers functionality.

Details

Type: boolean
Default: false
Example: true

Server Options

`services.mcpServers.servers..command`

Command to run the MCP server.

Details

Type: string
Default: "npx"
Example: "/path/to/custom/command"

`services.mcpServers.servers..enable`

Enable or disable this MCP server configuration.

Details

Type: boolean
Default: false
Example: true

`services.mcpServers.servers..env`

Environment variables to set when running the server.

Details

Type: attribute set of strings
Default: {}
Example: { GITHUB_PERSONAL_ACCESS_TOKEN = "ghp_abcdef123456"; }

`services.mcpServers.servers..filesystem.args`

Default arguments for the filesystem MCP server.

Details

Type: list of strings
Default: ["-y", "@modelcontextprotocol/server-filesystem"]

`services.mcpServers.servers..filesystem.extraArgs`

Directories to provide access to.

Details

Type: list of strings
Example: ["/home/user/Documents", "/home/user/Projects"]

`services.mcpServers.servers..type`

Type of MCP server.

Details

Type: string
Example: "filesystem" or "github"

Client Options

`services.mcpServers.clients..clientType`

Type of MCP client to configure.

Details

Type: string, one of "claudeDesktop", "cursor"
Default: Depends on the client name
Example: "claudeDesktop"

`services.mcpServers.clients..configPath`

Path to the client configuration file. If not specified, a default path will be used.

Details

Type: string
Default: ""
Example: "~/Library/Application Support/Claude/claude_desktop_config.json"

`services.mcpServers.clients..enable`

Whether to enable this MCP client configuration.

Details

Type: boolean
Default: false
Example: true

`services.mcpServers.clients..servers`

List of MCP server names to enable for this client.

Details

Type: list of strings
Default: []
Example: ["filesystem", "github"]

Example Configuration

{
  services.mcpServers = {
    enable = true;

    servers.filesystem = {
      enable = true;
      type = "filesystem";
      command = "npx";
      filesystem.extraArgs = [
        "/home/user/projects"
        "/home/user/documents"
      ];
    };

    servers.github = {
      enable = true;
      type = "github";
      command = "npx";
      env.GITHUB_PERSONAL_ACCESS_TOKEN = "ghp_yourtokenhere";
    };

    clients.claude = {
      enable = true;
      clientType = "claudeDesktop";
      servers = [ "filesystem" "github" ];
    };

    clients.cursor = {
      enable = true;
      clientType = "cursor";
      servers = [ "filesystem" ];
    };
  };
}

Source Code

For more details, check out the source code on GitHub.