MCP server PostgreSQL

postgresql-mcp

An MCP (Model Context Protocol) server that gives AI assistants structured, read-optimized access to PostgreSQL databases. It exposes schema exploration, data profiling, relationship analysis, query explanation, and safe read/write operations through a standardized MCP interface.

Features

• 24 MCP tools covering schema search, table description, data profiling, relationship/dependency inspection, query explanation, connection testing, schema/extension/view/trigger listing, CREATE TABLE DDL generation, table sizing, and tiered write access
• Tiered access model via POSTGRESQL_ACCESS_LEVEL: READONLY (default), DML-RW (adds insert/update/delete), DDL-RW (adds create/drop table/index)
• SQL-safe design with identifier validation, exact named-parameter binding, single-statement checks, and database-enforced read-only transactions
• Authoritative row limits that cap read_data results even when the submitted query contains its own larger LIMIT
• Mutation confirmation with preview mode that shows affected rows before executing writes when POSTGRESQL_REQUIRE_CONFIRMATION is enabled
• Explain plan via EXPLAIN (FORMAT JSON) for understanding query performance
• Connection testing that validates connectivity and reports latency
• Environment listing showing current host, database, and access-level configuration
• Optional HTTP bearer authentication, same-origin protection, request-size limits, and graceful shutdown

Installation

Download the latest release for your platform from the Releases page.

Usage

Environment Variables

Variable	Required	Default	Description
POSTGRESQL_HOST	Yes	—	PostgreSQL hostname or IP
POSTGRESQL_DATABASE	Yes	—	Database name
POSTGRESQL_USER	Yes	—	Login username
POSTGRESQL_PASSWORD	Yes	—	Login password
POSTGRESQL_PORT	No	5432	PostgreSQL port
POSTGRESQL_SSLMODE	No	prefer	SSL mode: disable, allow, prefer, require, verify-ca, verify-full
POSTGRESQL_ACCESS_LEVEL	No	READONLY	READONLY, DML-RW, or DDL-RW
POSTGRESQL_CONNECTION_TIMEOUT	No	30	Connection timeout in seconds
POSTGRESQL_QUERY_TIMEOUT	No	120	Query timeout in seconds
POSTGRESQL_MAX_ROWS_DEFAULT	No	1000	Default row limit for queries
POSTGRESQL_REQUIRE_CONFIRMATION	No	true	Require confirm flag for writes
POSTGRESQL_TRANSPORT	No	stdio	MCP transport: stdio or http
POSTGRESQL_HTTP_ADDR	No	127.0.0.1:8080	HTTP listen address when POSTGRESQL_TRANSPORT=http
POSTGRESQL_HTTP_PATH	No	/mcp	Stateless Streamable HTTP endpoint path when POSTGRESQL_TRANSPORT=http
POSTGRESQL_HTTP_BEARER_TOKEN	No	—	Require Authorization: Bearer <token> for HTTP requests

Running as an MCP Server

By default, the server communicates over stdio. Configure your MCP client to launch it:

{
  "mcpServers": {
    "postgresql": {
      "command": "/path/to/bin/postgresql-mcp",
      "env": {
        "POSTGRESQL_HOST": "localhost",
        "POSTGRESQL_DATABASE": "YourDatabase",
        "POSTGRESQL_USER": "postgres",
        "POSTGRESQL_PASSWORD": "YourPassword",
        "POSTGRESQL_SSLMODE": "disable",
        "POSTGRESQL_ACCESS_LEVEL": "READONLY"
      }
    }
  }
}

To serve MCP using the stateless Streamable HTTP transport, set POSTGRESQL_TRANSPORT=http:

POSTGRESQL_TRANSPORT=http \
POSTGRESQL_HTTP_ADDR=127.0.0.1:8080 \
POSTGRESQL_HTTP_PATH=/mcp \
/path/to/bin/postgresql-mcp

Then configure a Streamable HTTP MCP client to connect to:

http://localhost:8080/mcp

Set POSTGRESQL_HTTP_BEARER_TOKEN when the endpoint is reachable by anything other than a trusted local client. Binding to a non-loopback address without authentication exposes every tool allowed by POSTGRESQL_ACCESS_LEVEL.

Access Levels

• READONLY (default) — Schema exploration, data reading, profiling, relationship inspection, query explanation, connection testing, schema listing, extensions, views, triggers, CREATE TABLE DDL generation, table sizing. 18 tools.
• DML-RW — All read-only tools plus insert_data, update_data, delete_data. 21 tools.
• DDL-RW — All DML tools plus create_table, create_index, drop_table. 24 tools.

Mutations (update_data, delete_data, drop_table) require a "confirm": true flag when POSTGRESQL_REQUIRE_CONFIRMATION is enabled (the default). Without confirmation, the server returns a preview of the affected rows instead.

update_data and delete_data predicates use named placeholders. For example, use "where": "id = $id AND tenant = $tenant" with "params": {"id": 42, "tenant": "acme"}. Every placeholder must have a value and every supplied parameter must be used.

Query results decode json/jsonb into structured JSON, encode bytea as base64, and suffix duplicate column names (id, id_2, and so on) so joined results do not silently lose values.

MCP Tools

Read-Only (READONLY)

Tool	Description
search_schema	Search tables and columns by name pattern with pagination
describe_table	Get columns, primary keys, foreign keys, and indexes for a table
list_table	List tables, optionally filtered by schema and name
list_databases	List all databases on the server
list_environments	Show current connection and access-level configuration
profile_table	Row count, null counts, distinct counts, min/max when supported, with optional data samples
inspect_relationships	List foreign keys going out of and into a table
inspect_dependencies	Find objects (views, functions) that depend on a table
explain_query	Get the JSON execution plan for a read-only query
read_data	Execute a read-only SELECT query with row limits
test_connection	Ping the server and return latency and server version info
validate_environment_config	Validate that all environment variables are correctly configured
list_schemas	List all user schemas with owner and description
list_extensions	List installed PostgreSQL extensions with version
list_views	List views with their SQL definitions
list_triggers	List triggers with event, timing, and definition
show_create_table	Generate CREATE TABLE DDL including defaults, generated/identity columns, and table constraints
table_size	Table and index sizes, toast size, and estimated row counts, optionally for one table

DML (DML-RW)

Tool	Description
insert_data	Insert one or more rows into a table
update_data	Update rows matching a WHERE clause (with optional preview)
delete_data	Delete rows matching a WHERE clause (with optional preview)

DDL (DDL-RW)

Tool	Description
create_table	Create a table with column definitions, primary keys, and identity columns
create_index	Create a standard or unique index on specified columns
drop_table	Drop a table (with optional preview/confirmation)

License

MIT License. See LICENSE for details.