gem-hunter

A Model Context Protocol server for PostgreSQL databases. Enables LLMs to query and analyze PostgreSQL databases through a controlled interface.

Add to your MCP client settings:

{
  "mcpServers": {
    "postgres": {
      "command": "npx",
      "args": ["--yes", "pg-mcp-server", "--transport", "stdio"],
      "env": {
        "DATABASE_URL": "postgresql://postgres:postgres@localhost:5432/postgres"
      }
    }
  }
}

• DATABASE_URL - PostgreSQL connection string (required)
• DANGEROUSLY_ALLOW_WRITE_OPS - Enable writes (default: false)
• DEBUG - Enable debug logging (default: false)
• PG_SSL_ROOT_CERT - Optional path to a TLS CA bundle (e.g., AWS RDS global bundle)

• Default transport is stdio. Switch to HTTP with the --transport flag.
• HTTP mode serves the MCP Streamable HTTP endpoint at /mcp on PORT (default 3000).
• Clients that support Streamable HTTP should connect to http://localhost:3000/mcp.

Start commands:

# stdio transport (default, via installed CLI)
pg-mcp-server --transport=stdio

# http transport
pg-mcp-server --transport=http

• query - Execute SQL queries

  { "sql": "SELECT * FROM users WHERE active = true LIMIT 10" }

• postgres://tables - List all tables
• postgres://table/{schema}/{table} - Get table schema and sample data

Here's an example prompt to test if your MCP server is working:

Show me the first 5 users from the database

For data analysis and exploration, I've added a Cursor rule for using the MCP server together with notebooks in .cursor/rules/notebooks.mdc:

# Start PostgreSQL with sample data
bun run db:start

# Test with MCP Inspector
bun run inspector

# Stop PostgreSQL
bun run db:stop

Sample tables included: users, products, orders, order_items

# Clone and install
git clone https://github.com/ericzakariasson/pg-mcp-server.git
cd pg-mcp-server
bun install

# Run (stdio transport)
bun run index.ts -- --transport=stdio
DEBUG=true bun run index.ts -- --transport=stdio

# Run (http transport)
bun run index.ts -- --transport=http
DEBUG=true bun run index.ts -- --transport=http
bun test                      # Run tests

Use local build in MCP client settings:

bun run build:js

{
  "mcpServers": {
    "postgres": {
      "command": "node",
      "args": ["/absolute/path/to/pg-mcp-server/lib/index.js", "--transport", "stdio"],
      "env": {
        "DATABASE_URL": "postgresql://postgres:postgres@localhost:5432/postgres"
      }
    }
  }
}

This repo auto-creates a GitHub Release when you push a tag that matches the version in package.json:

1. Update CHANGELOG.md and bump the version in package.json.
2. Commit the changes on main (or your release branch).
3. Create and push a matching tag:

VERSION=$(jq -r .version package.json)
git tag v"$VERSION"
git push origin v"$VERSION"

The GitHub Actions workflow will validate that the tag (e.g. v0.1.0) matches package.json, then use gh to create a release with generated notes, and publish to npm.

MIT - see LICENSE