yhosok/tbls-mcp-server

tbls MCP Server

⚠️ EXPERIMENTAL SOFTWARE This application is experimental software with insufficient testing coverage (~66% currently). It is not suitable for production use. We recommend experimental use only for development and testing purposes. If you plan to use it in production, please conduct thorough testing beforehand.

A Model Context Protocol (MCP) server that provides access to database schema information generated by tbls and enables SQL query execution on MySQL and SQLite databases.

Features

• JSON Schema Support: Primary support for tbls-generated JSON schema files with optimal performance
• JSON-Only Support: Uses JSON schema format from tbls for optimal performance
• Multiple Resource Types: Access schemas, tables, and index information through MCP resources
• SQL Query Execution: Execute SELECT queries on MySQL and SQLite databases with comprehensive security
• Type Safety: Full TypeScript implementation with zod validation
• Error Handling: Robust error handling using neverthrow Result types
• MCP Compatible: Works with Claude Desktop and other MCP clients
• Flexible Configuration: Support for both CLI arguments and configuration files

MCP Client Configuration

To use this server with MCP clients, add the following configuration to your MCP client's configuration file.

Example: Claude Desktop

Add to your Claude Desktop configuration file (claude_desktop_config.json):

{
  "mcpServers": {
    "tbls": {
      "command": "npx",
      "args": [
        "github:yhosok/tbls-mcp-server",
        "--schema-source", "/path/to/your/tbls/schema.json",
        "--database-url", "mysql://user:password@localhost:3306/database"
      ]
    }
  }
}

Note: You can create a .tbls-mcp-server.json configuration file to specify server options (see Configuration section below) and use just the command without arguments in your MCP client configuration.

Installation

Prerequisites

• Node.js 18 or higher
• tbls installed and configured
• Database access (MySQL or SQLite) - optional for SQL query features

Via npx (Recommended for MCP)

npx github:yhosok/tbls-mcp-server --schema-source /path/to/tbls/schema.json

Clone and Run Locally

git clone https://github.com/yhosok/tbls-mcp-server.git
cd tbls-mcp-server
npm install
npm run build

# Run the server
node dist/index.js --schema-source /path/to/tbls/schema.json

Usage

Basic Usage (Schema Information Only)

npx github:yhosok/tbls-mcp-server --schema-source /path/to/tbls/schema.json

With Database Connection (Full Features)

npx github:yhosok/tbls-mcp-server \
  --schema-source /path/to/tbls/schema.json \
  --database-url mysql://user:pass@localhost:3306/mydb

Using Configuration File

npx github:yhosok/tbls-mcp-server --config .tbls-mcp-server.json

JSON Schema Sample

Example of a tbls-generated JSON schema file structure:

{
  "name": "myapp",
  "type": "mysql",
  "tables": [
    {
      "name": "users",
      "type": "table",
      "comment": "User accounts",
      "columns": [
        {
          "name": "id",
          "type": "int(11)",
          "nullable": false,
          "primary": true,
          "comment": "Primary key"
        },
        {
          "name": "email",
          "type": "varchar(255)",
          "nullable": false,
          "unique": true,
          "comment": "User email address"
        }
      ],
      "indexes": [
        {
          "name": "PRIMARY",
          "columns": ["id"],
          "unique": true
        },
        {
          "name": "idx_email",
          "columns": ["email"],
          "unique": true
        }
      ]
    }
  ]
}

Examples

Setting up with tbls

First, install tbls by following the instructions at https://github.com/k1LoW/tbls.

Then generate schema documentation:

# Generate schema documentation (default output: ./dbdoc)
tbls doc mysql://user:pass@localhost:3306/mydb

# Or generate JSON schema directly
tbls out -t json mysql://user:pass@localhost:3306/mydb -o ./custom/schema/path/schema.json

# Start MCP server
npx github:yhosok/tbls-mcp-server --schema-source ./dbdoc/schema.json

Directory Structure

Expected tbls output structure:

./dbdoc/
├── schema.json              # Complete schema information (required)
└── README.md               # Human-readable overview (optional)

Note:

• Use tbls out -t json to generate the JSON schema file
• The default output file is schema.json in the specified directory
• The --schema-source option can point to either a JSON file or directory containing JSON files

Using with Claude Desktop

1. Configure Claude Desktop:

   {
     "mcpServers": {
       "tbls": {
         "command": "npx",
         "args": [
           "github:yhosok/tbls-mcp-server",
           "--schema-source", "/Users/username/projects/myapp/dbdoc/schema.json",
           "--database-url", "mysql://user:password@localhost:3306/myapp"
         ]
       }
     }
   }
   

2. Restart Claude Desktop and the tbls server will be available

3. Query your database schema:

   • "Show me all tables in the database"
   • "What columns does the users table have?"
   • "Show me the relationship between users and posts"
   • "Execute: SELECT COUNT(*) FROM users WHERE active = true"

Common SQL Queries

Schema exploration:

-- MySQL
SHOW TABLES;
SHOW COLUMNS FROM users;
SELECT * FROM information_schema.table_constraints WHERE table_name = 'users';

-- SQLite
SELECT name FROM sqlite_master WHERE type='table';
PRAGMA table_info(users);

Data analysis:

-- User statistics
SELECT
  COUNT(*) as total_users,
  COUNT(CASE WHEN active = 1 THEN 1 END) as active_users,
  COUNT(CASE WHEN created_at > DATE_SUB(NOW(), INTERVAL 30 DAY) THEN 1 END) as recent_users
FROM users;

-- Popular posts
SELECT p.title, p.created_at, COUNT(c.id) as comment_count
FROM posts p
LEFT JOIN comments c ON p.id = c.post_id
GROUP BY p.id
ORDER BY comment_count DESC
LIMIT 10;

MCP Resources

The server exposes tbls-generated schema information through the following MCP resources:

MCP Tools

The server provides SQL query execution capabilities when a database connection is configured:

SQL Query Tool (execute-sql)

Purpose: Execute SELECT queries on connected MySQL or SQLite databases with comprehensive security features.

Security Features:

• ✅ SELECT queries only - INSERT, UPDATE, DELETE, DROP, etc. are blocked
• ✅ Parameterized queries prevent SQL injection attacks
• ✅ Query timeout protection prevents long-running queries
• ✅ Multiple statement prevention blocks compound SQL injection
• ✅ Input sanitization removes dangerous patterns

Supported Databases:

• MySQL (via connection string or individual parameters)
• SQLite (file path or :memory: database)

Parameters:

• query (required): SQL SELECT query to execute
• parameters (optional): Array of parameters for prepared statements
• timeout (optional): Query timeout in milliseconds (1000-300000, default: 30000)

Usage Examples:

{
  "query": "SELECT * FROM users WHERE active = ?",
  "parameters": [true]
}

{
  "query": "SELECT u.name, COUNT(p.id) as post_count FROM users u LEFT JOIN posts p ON u.id = p.user_id GROUP BY u.id",
  "parameters": []
}

{
  "query": "SHOW TABLES",
  "parameters": [],
  "timeout": 10000
}

Response Format:

{
  "rows": [
    {"id": 1, "name": "John Doe", "email": "john@example.com"},
    {"id": 2, "name": "Jane Smith", "email": "jane@example.com"}
  ],
  "rowCount": 2,
  "columns": [
    {"name": "id", "type": "int"},
    {"name": "name", "type": "varchar"},
    {"name": "email", "type": "varchar"}
  ]
}

Configuration

Command Line Arguments

• --schema-source <path>: Path to tbls JSON schema file or directory (required)
• --database-url <url>: Database connection string (optional)
• --log-level <level>: Set logging level (debug, info, warn, error, default: info)
• --config <path>: Path to configuration file
• --help: Show help information
• --version: Show version information

Environment Variables

• TBLS_SCHEMA_SOURCE: Path to tbls JSON schema file or directory
• DATABASE_URL: Database connection string (optional)
• LOG_LEVEL: Logging level (debug, info, warn, error)

Configuration File

Create a .tbls-mcp-server.json file in your project root:

{
  "schemaSource": "/path/to/tbls/schema.json",
  "logLevel": "info",
  "database": {
    "type": "mysql",
    "connectionString": "mysql://username:password@localhost:3306/database_name"
  }
}

Database Configuration Options

MySQL:

{
  "database": {
    "type": "mysql",
    "connectionString": "mysql://user:password@host:port/database"
  }
}

SQLite:

{
  "database": {
    "type": "sqlite",
    "connectionString": "sqlite:///path/to/database.db"
  }
}

Complete Configuration Examples

Production Setup with JSON Schema:

{
  "schemaSource": "/opt/app/schema/production.json",
  "logLevel": "warn",
  "database": {
    "type": "mysql",
    "connectionString": "mysql://readonly_user:password@db.company.com:3306/production_db"
  }
}

Development Setup with Local Files:

{
  "schemaSource": "./dbdoc/schema.json",
  "logLevel": "debug",
  "database": {
    "type": "sqlite",
    "connectionString": "sqlite:///./dev.db"
  }
}

Troubleshooting

Common Issues

Server fails to start:

• Verify Node.js version (18+ required)
• Check that the schema source file exists or directory contains tbls-generated files
• For JSON: Ensure the JSON file is valid and contains proper schema structure
• For directories: Ensure the directory contains proper .json files
• Ensure database connection string is valid (if using database features)

No resources available:

• Confirm tbls has generated JSON schema file in the specified location
• Check file permissions on the schema file/directory
• Enable debug logging: --log-level debug

Database connection issues:

• Test database connectivity outside of the MCP server
• Verify connection string format
• Check firewall and network access
• Ensure database user has appropriate permissions (SELECT at minimum)

SQL queries fail:

• Only SELECT statements are allowed
• Use parameterized queries with ? placeholders
• Check query timeout settings
• Review query syntax for your database type

Claude Desktop integration issues:

• Restart Claude Desktop after configuration changes
• Check configuration file syntax (valid JSON)
• Verify file paths are absolute and accessible
• Check Claude Desktop logs for error messages

Debug Mode

Enable debug logging to troubleshoot issues:

tbls-mcp-server --schema-source /path/to/schema.json --log-level debug

This will output detailed information about:

• Configuration loading and schema source resolution
• Resource discovery (JSON file vs directory detection)
• Database connections
• SQL query execution
• Error details and diagnostics

Support

For issues and questions:

• Check the GitHub Issues
• Review tbls documentation
• Consult MCP specification

Development

Prerequisites

• Node.js 18+
• npm or yarn

Setup

git clone https://github.com/yhosok/tbls-mcp-server.git
cd tbls-mcp-server
npm install

Development Commands

# Start development server
npm run dev

# Run tests
npm test

# Run tests with coverage
npm run test:coverage

# Build for production
npm run build

# Run linter
npm run lint

Testing

The project uses Jest for testing with a focus on Test-Driven Development (TDD):

# Run all tests
npm test

# Run tests in watch mode
npm run test:watch

# Generate coverage report
npm run test:coverage

Architecture

The server is built using:

• TypeScript: Type-safe implementation
• @modelcontextprotocol/sdk: Official MCP SDK
• neverthrow: Result types for error handling
• zod: Schema validation
• mysql2: MySQL database connectivity
• sqlite3: SQLite database connectivity

Security

• Only SELECT statements are permitted for SQL execution
• Input validation using zod schemas
• SQL injection prevention through parameterized queries
• Connection string validation and sanitization

Contributing

1. Fork the repository
2. Create a feature branch
3. Write tests for your changes
4. Implement your changes
5. Ensure all tests pass
6. Submit a pull request

License

ISC License

Related Projects

• tbls - Schema documentation tool
• Model Context Protocol - Protocol specification