tusk-mcp

PostgreSQL MCP server for AI agents. Exposes schema introspection and SELECT-only query execution over the Model Context Protocol, with write access opt-in per target.

Install

# npx (no install needed)
npx tusk-mcp --host db.example.com --database mydb

# or clone + run
bun install
bun run src/index.ts --host localhost --database mydb

Setup UI

Interactive browser-based setup that generates config for Claude Desktop, Claude Code, Cursor, Windsurf, and OpenAI Codex.

npx tusk-mcp setup

Build standalone binary

bun run build           # Windows
bun run build:linux     # Linux
bun run build:macos     # macOS ARM

Connection

Individual flags (recommended)

tusk-mcp --host db.example.com --port 5432 --user admin --password 'p@ss' --database mydb

Connection string

tusk-mcp --connection-string "postgres://admin:p%[email protected]:5432/mydb"

Unencoded special characters in passwords (@, #) are handled automatically.

Environment variables

PGHOST=db.example.com PGDATABASE=mydb tusk-mcp

Priority: flags > --connection-string > DATABASE_URL > PG* env vars

Multiple environments / databases

A config file defines named targets: environments (local/stage/prod) or entirely different databases within one app. tusk.config.jsonc or tusk.config.json in the working directory is picked up automatically when no connection flags are given; --config <path> (relative or absolute) loads an explicit file. Connection flags cannot be combined with a config file.

{
  "defaultTarget": "local",          // used when a tool call omits target
  "defaults": {                      // merged under every target
    "user": "app",
    "database": "myapp"
  },
  "targets": {
    "local": { "host": "localhost", "access": "write", "description": "dev" },
    "stage": {
      "host": "stage.db.internal",
      "password": "${STAGE_DB_PASSWORD}",   // env var interpolation
      "ssl": true
    },
    "prod": {
      "connectionString": "postgres://ro:${PROD_DB_PASSWORD}@10.0.0.5:5432/myapp",
      "ssh": { "host": "bastion.example.com", "user": "deploy", "key": "~/.ssh/id_rsa" },
      "access": "structure",                // schema visible, queries disabled
      "description": "production"
    },
    "analytics": { "host": "warehouse.db", "database": "events" }
  }
}

Target fields mirror the CLI flags: host, port, user, password, passwordFile, passwordCmd, database, connectionString, ssl (true or {ca, cert, key} paths), ssh ({host, port, user, key, password}), access, description. structureOnly: true is still read as access: "structure"; setting both to different levels is a config error.

Priority: explicit fields > connectionString > defaults. ssh/ssl objects deep-merge, so defaults.ssh can hold the shared bastion and a target override just the port. ${VAR} interpolates from the environment in any string, so the file is safe to commit. Config-file targets ignore PG* env vars; use ${PGPASSWORD} explicitly if wanted.

With multiple targets every tool takes a target enum parameter (optional when defaultTarget is set, absent entirely with a single target), the target list is announced via MCP instructions, and compare-schemas becomes available. Connections are lazy per target: an unreachable bastion never blocks startup or the other targets.

Password security

# From file (Docker/K8s secrets)
tusk-mcp --host db --database mydb --password-file /run/secrets/db_pass

# From command (any secrets manager)
tusk-mcp --host db --database mydb --password-cmd 'vault kv get -field=password secret/db'
tusk-mcp --host db --database mydb --password-cmd 'op read op://vault/db/password'

SSL

Providing any certificate file automatically enables SSL.

tusk-mcp --host db --database mydb --ssl-ca /path/to/ca.crt       # CA verification
tusk-mcp --host db --database mydb \                               # mutual TLS
  --ssl-ca ca.crt --ssl-cert client.crt --ssl-key client.key

SSH tunnel

tusk-mcp --host db-internal --database mydb \
  --ssh-host bastion.example.com --ssh-user deploy --ssh-key ~/.ssh/id_rsa

Access levels

Each target has one access level, read by default.

| access | Tools | Connection | |---|---|---| | structure | overview, describe-tables | read-only transactions | | read | plus execute-query | read-only transactions | | write | plus execute-write | writes allowed, through execute-write only |

tusk-mcp --host db --database mydb --structure-only   # every target: structure
tusk-mcp --host db --database mydb --allow-writes     # every target: write

The two flags are mutually exclusive. --structure-only also narrows a config file, but --allow-writes is rejected alongside one: escalating a target to writes has to be written in the file, where it is reviewable, rather than in an MCP client's command line.

execute-query cannot mutate on any target, write-enabled ones included: every query runs inside a READ ONLY transaction, so a SELECT that hides an INSERT behind a volatile function is refused by the server, not just by the SQL parser. read and structure connections additionally start with default_transaction_read_only. Writes therefore only ever happen through execute-write, which is registered only when some target allows them and whose target parameter lists write-enabled targets only.

execute-write takes one statement per call, reports the affected row count, and previews RETURNING rows. Beyond the target gate it does not filter SQL: on a write target the database role is the boundary, so give that role only the privileges the agent should have.

Tools

| Tool | Description | |---|---| | overview | All schemas with tables, views, and estimated row counts in one call (partitions filtered out) | | describe-tables | Columns, types, PKs, FKs, and enum values for one or more tables per call | | execute-query | Read-only SQL with limit (rejected on structure-only targets) | | execute-write | One mutating statement with affected rows and RETURNING preview (write-enabled targets only) | | compare-schemas | Structural diff of a schema between two targets (multi-target only) |

Output format

Tool results use compact text in content for the AI model and JSON-safe preview data in structuredContent for clients that support structured MCP output. Query text uses a tab-delimited preview with null=\N; strings are JSON-quoted, so empty strings render as "" and the literal string "\\N" is distinct from SQL null. With multiple targets, results start with a target=<name> line.

MCP config

{
  "mcpServers": {
    "tusk": {
      "command": "npx",
      "args": ["-y", "tusk-mcp", "--host", "localhost", "--database", "mydb"]
    }
  }
}

Claude Code

claude mcp add --transport stdio tusk -- npx -y tusk-mcp --host localhost --database mydb

OpenAI Codex (~/.codex/config.toml)

[mcp_servers.tusk]
command = "npx"
args = ["-y", "tusk-mcp", "--host", "localhost", "--database", "mydb"]

All flags

| Flag | Type | Default | Description | |---|---|---|---| | --config | string | - | Multi-target config file (see above) | | --host | string | localhost | PostgreSQL host | | --port | number | 5432 | PostgreSQL port | | --user | string | - | Database user | | --password | string | - | Database password | | --password-file | string | - | Read password from file | | --password-cmd | string | - | Run command for password | | --database | string | - | Database name | | --connection-string | string | - | Full connection URL | | --ssl | boolean | false | Enable SSL without certificate verification | | --ssl-ca | string | - | CA certificate path (enables SSL) | | --ssl-cert | string | - | Client certificate path (enables SSL) | | --ssl-key | string | - | Client key path (enables SSL) | | --ssh-host | string | - | SSH tunnel host | | --ssh-port | number | 22 | SSH tunnel port | | --ssh-user | string | - | SSH username | | --ssh-key | string | - | SSH private key path | | --ssh-password | string | - | SSH password | | --structure-only | boolean | false | Schema only, no execute-query | | --allow-writes | boolean | false | Add execute-write (no config file) |