PgLLens

What it does

PgLLens connects any PostgreSQL database to AI assistants via the Model Context Protocol. It gives AI models 19 purpose-built tools to discover, understand, and query your data — entirely in read-only mode. Beyond basic schema listing, PgLLens auto-extracts PostgreSQL comments, constraints, enums, triggers, and view definitions, making your AI assistant aware of your schema the way your engineering team is. You can also inject a plain-markdown domain context file to embed business rules and query patterns directly into every tool response.

Tools

• query — Execute read-only SELECT queries; results as markdown tables with row counts
• explain_query — EXPLAIN / EXPLAIN ANALYZE for query planning and performance tuning
• validate_query — Syntax and reference check without executing
• list_tables — Tables and views with descriptions and row counts
• describe_table — Column types, nullability, defaults, PKs, FKs, comments
• schema_overview — Full database schema as a markdown summary
• get_ontology — Semantic layer: CHECK constraints, ENUMs, unique keys, view definitions, indexes, triggers, and injected domain context
• get_relationships — FK relationship map; outputs text or Mermaid ER diagram
• get_sample_data — Sample rows (1–20) from any table
• search_columns — Cross-table column search by name pattern
• get_table_stats — Row counts, null %, distinct values per column
• get_table_health — Vacuum/analyze history, dead tuples, index usage stats
• list_hypertables — TimescaleDB hypertable details, chunk intervals, compression policies
• Plus list_functions, get_view_definition, get_function_source, list_extensions, list_roles, refresh_schema

Installation

Claude Desktop (claude_desktop_config.json):

{
  "mcpServers": {
    "pgllens": {
      "url": "http://localhost:3000/mcp"
    }
  }
}

Start the server first:

docker run -p 3000:3000 -e DATABASE_URL="postgresql://user:pass@host:5432/mydb" dmdufresne/pgllens:latest

With OAuth:

{
  "mcpServers": {
    "pgllens": {
      "url": "http://localhost:3000/mcp",
      "authorizationUrl": "http://localhost:3000/oauth/authorize",
      "tokenUrl": "http://localhost:3000/oauth/token"
    }
  }
}

Supported hosts

Claude Desktop and Claude Code are explicitly confirmed in the README. Cursor, Windsurf, and VS Code are also listed as compatible clients.