Pg Pool

A single MCP server for all your Postgres databases.

Instead of configuring a separate MCP server entry for each database, pg-pool-mcp lets you define all your connections in one config file and query any of them by name. No restarts, no config juggling.

Why?

The official Postgres MCP server binds to a single database via a CLI argument. If you work with multiple databases (dev, staging, prod, or just different projects), you either need multiple MCP server entries or you're editing config and restarting every time you switch.

pg-pool-mcp gives you:

• One MCP server, many databases -- configure once, query any database by name
• Lazy connection pooling -- connects on first use, not at startup
• Read-only by default -- queries are wrapped in read-only transactions unless you opt in to writes
• Query timeouts -- prevents runaway queries from hanging your session
• Environment variable interpolation -- keep secrets out of your config file

Setup

git clone <repo-url>
cd pg-pool-mcp
npm install

Configuration

Create a databases.json file (see databases.example.json for reference):

{
  "databases": {
    "local": {
      "host": "localhost",
      "port": 5432,
      "database": "mydb",
      "user": "postgres",
      "password": "$PG_PASSWORD",
      "readOnly": false
    },
    "production": {
      "connectionString": "postgresql://$PROD_USER:$PROD_PASSWORD@prod-host:5432/prod_db",
      "readOnly": true
    }
  },
  "defaults": {
    "readOnly": true,
    "queryTimeout": 30000,
    "poolSize": 5
  }
}

Each database entry supports either a connectionString or individual fields (host, port, database, user, password).

Per-database options

Option	Type	Default	Description
readOnly	boolean	true	Wrap queries in read-only transactions
queryTimeout	number	30000	Statement timeout in milliseconds
poolSize	number	5	Max connections in the pool
ssl	boolean/object	—	SSL configuration passed to pg

Environment variable interpolation

String values support $VAR and ${VAR} syntax, resolved from your environment at startup. This keeps passwords out of the config file:

{
  "password": "$PG_PASSWORD",
  "connectionString": "postgresql://${DB_USER}:${DB_PASS}@host/db"
}

Register with Claude Code

Add to ~/.claude.json (global) or .mcp.json (per-project):

{
  "mcpServers": {
    "multi-pg": {
      "type": "stdio",
      "command": "npx",
      "args": [
        "tsx",
        "/path/to/pg-pool-mcp/src/index.ts",
        "--config",
        "/path/to/databases.json"
      ]
    }
  }
}

You can also set the config path via environment variable:

{
  "mcpServers": {
    "multi-pg": {
      "type": "stdio",
      "command": "npx",
      "args": ["tsx", "/path/to/pg-pool-mcp/src/index.ts"],
      "env": {
        "MULTI_PG_MCP_CONFIG": "/path/to/databases.json"
      }
    }
  }
}

Restart Claude Code after adding the config.

Tools

list_databases

Lists all configured databases with their connection status and read-only setting. Call this first to see available database names.

query

Run a SQL query against a named database.

• database -- name from your config (e.g. "local", "production")
• sql -- the SQL to execute

If the database is configured as readOnly: true, queries are wrapped in BEGIN TRANSACTION READ ONLY and rolled back automatically. Write attempts will fail.

list_tables

List all tables in a database with estimated row counts.

• database -- name from your config
• schema -- schema to list (default: "public")

describe_table

Get the full schema of a table: columns, types, nullability, defaults, primary keys, and foreign keys.

• database -- name from your config
• table -- table name
• schema -- schema name (default: "public")

Development

# Type-check
npx tsc --noEmit

# Run directly
npx tsx src/index.ts --config databases.json

# Build
npm run build

License

ISC