mcpgen

A code generator for MCP (Model Context Protocol) tool servers. Scaffolds complete Go projects with a full JSON-RPC server, CLI mode, build system, and Claude Code integration — ready to run with a single just build.

Features

• Generates a complete, working MCP tool server in Go (stdio transport)
• Dual-mode operation: runs as an MCP server or a standalone CLI tool
• Configurable tool parameters with JSON Schema types
• Produces ready-to-use build files (justfile, go.mod, .mcp.json)
• Pre-configured Claude Code integration (.claude/settings.local.json)
• Refuses to overwrite existing projects

Prerequisites

• Go 1.23+
• just (command runner)
• macOS (generates codesign step in justfile)

Installation

git clone https://github.com/hegner123/mcpgen.git
cd mcpgen
just install

This builds the binary, signs it, and copies it to /usr/local/bin/.

Usage

As an MCP Server

Add mcpgen to your Claude Code configuration:

claude mcp add mcpgen -- mcpgen

Then invoke it through Claude Code by asking it to generate a new MCP tool.

Parameters:

Name	Type	Required	Description
name	string	yes	Tool name (used for binary, module, and MCP server name)
description	string	yes	One-line description of what the tool does
params	array	yes	Array of parameter definitions for the generated tool
output_dir	string	no	Directory to create the project in (default: ~/Documents/Code/terse-mcp/<name>)
module	string	no	Go module path (default: github.com/hegner123/<name>)

Each entry in params is an object:

Field	Type	Description
name	string	Parameter name
type	string	JSON Schema type: string, boolean, integer, number, array, object
description	string	Parameter description
required	boolean	Whether the parameter is required
default	any	Default value (optional)

As a CLI Tool

mcpgen --cli \
  --name mytool \
  --description "Does something useful" \
  --params '[{"name":"input","type":"string","description":"Input file path","required":true}]'

Flags:

Flag	Description
--cli	Run in CLI mode (required for direct invocation)
--name	Tool name (required)
--description	Tool description (required)
--output-dir	Output directory (optional)
--module	Go module path (optional)
--params	Tool parameters as a JSON array (optional)

Generated Project Structure

<name>/
├── main.go                      # Full MCP server + CLI with your parameters
├── go.mod                       # Go module definition
├── justfile                     # Build, install, clean, test targets
├── .mcp.json                    # MCP server registration for Claude Code
├── .gitignore                   # Go + IDE + OS ignores
└── .claude/
    └── settings.local.json      # Claude Code permission allowlist

The generated main.go includes:

• Complete MCP JSON-RPC server (initialize, tools/list, tools/call)
• CLI mode with flag parsing for all defined parameters
• Required parameter validation in both modes
• Signal handling (SIGINT/SIGTERM) for graceful shutdown
• A stub execute() function where you implement your tool logic

Example

Generate a tool that formats JSON files:

mcpgen --cli \
  --name jsonformat \
  --description "Format JSON files with consistent indentation" \
  --params '[
    {"name":"file","type":"string","description":"Path to JSON file","required":true},
    {"name":"indent","type":"integer","description":"Number of spaces for indentation","required":false,"default":2},
    {"name":"sort_keys","type":"boolean","description":"Sort object keys alphabetically","required":false}
  ]'

This creates ~/Documents/Code/terse-mcp/jsonformat/ with a complete MCP server. To start using it:

cd ~/Documents/Code/terse-mcp/jsonformat
just build
# Edit main.go — implement the execute() function
just install
claude mcp add jsonformat -- jsonformat

Contributing

See CONTRIBUTING.md for guidelines.

License

MIT