MCP Proto Generator

A standalone Model Context Protocol (MCP) server that generates Protocol Buffer (.proto) files from Diesel schema content. This allows Claude to generate protobuf definitions directly from Diesel table! macro definitions.

Features

• Standalone MCP Server: Works independently of any existing project
• Diesel to Proto Conversion: Converts Diesel table! macro definitions to Protocol Buffer definitions
• CRUD Operations: Generates complete CRUD request/response messages
• Type Mapping: Intelligent mapping from Diesel types to protobuf types
• Claude Integration: Direct integration with Claude Desktop

Installation

Install from Crates.io (Recommended):

cargo install mcp-diesel-proto-generator

The binary will be installed to ~/.cargo/bin/mcp-diesel-proto-generator.

Build from Source:

git clone <repository-url>
cd mcp-diesel-proto-generator
cargo build --release

Claude Desktop Configuration

Add the following to your Claude Desktop configuration file:

macOS: ~/Library/Application Support/Claude/claude_desktop_config.json Windows: %APPDATA%/Claude/claude_desktop_config.json

{
  "mcpServers": {
    "proto-generator": {
      "command": "/Users/yourusername/.cargo/bin/mcp-diesel-proto-generator",
      "args": []
    }
  }
}

Important: Replace /Users/yourusername with your actual home directory path, or use the full path where the binary is installed.

Usage with Claude

Once configured, you can use the following commands in Claude:

Generate Proto from Schema Content

Generate a proto file from this Diesel schema:

table! {
    users (id) {
        id -> Integer,
        email -> Text,
        name -> Nullable<Text>,
        created_at -> Timestamp,
        is_active -> Bool,
    }
}

table! {
    posts (id) {
        id -> Integer,
        user_id -> Integer,
        title -> Text,
        content -> Nullable<Text>,
        published_at -> Nullable<Timestamp>,
    }
}

Custom Package Name

Generate a proto file with package name "blog" from this schema:

[your schema here]

Supported Diesel Types

The MCP server maps Diesel types to protobuf types as follows:

Generated Proto Structure

The generated proto files include:

1. Entity Messages: One message per table with all fields
2. CRUD Request/Response Messages: Complete CRUD operations for each entity
3. Common Structures: Shared parameter and query structures
4. Service Definition: gRPC service with all CRUD operations
5. Timestamp Message: Custom timestamp representation

Example Output

For a users table, the generator creates:

• Users message (entity)
• CreateUsersRequest/Response
• GetUsersRequest/Response
• UpdateUsersRequest/Response
• DeleteUsersRequest/Response
• Service methods for all operations

Troubleshooting

MCP Server Not Found

• Ensure the binary path in claude_desktop_config.json is absolute and correct
• If installed via cargo install, the binary should be at ~/.cargo/bin/mcp-diesel-proto-generator
• Restart Claude Desktop after configuration changes

Schema Parsing Issues

• Ensure your Diesel schema is valid
• The parser expects standard table! macro definitions
• Make sure column definitions follow the format: column_name -> Type,

Permission Issues

• Ensure the binary has execute permissions: chmod +x target/release/mcp-proto-generator

Example Usage

You can test the MCP server with the provided example schema:

cat example_schema.rs | ./target/release/mcp-proto-generator

Development

To modify or extend the MCP server:

1. Clone the repository and edit src/main.rs
2. Rebuild with cargo build --release
3. Update your Claude Desktop configuration to point to the new binary
4. Restart Claude Desktop to pick up changes

License

This project is provided as-is for educational and development purposes.