db-gateway

DB Gateway MCP Server

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An MCP server that gives AI agents direct access to your databases — 145+ tools across 8 engines.

The point is that the agent reads your schema itself instead of you pasting DDL into a prompt:

You: "Find users who signed up last month and never placed an order"

  1. mysql_get_all_schemas          → reads every table definition
  2. mysql_get_table_relationships  → finds the users ↔ orders foreign key
  3. mysql_execute_query            → runs the LEFT JOIN

Engine	Tools	Engine	Tools
MySQL	16	Redis	21
PostgreSQL	16	DynamoDB	13
Redshift	27	Elasticsearch	19
MongoDB	14	Kafka	19

See It Work

Every screenshot below is one real session against a development MySQL database holding 249 rows — unedited output, not mock data. The agent calls a single tool, mysql_execute_query, and never sees a host, port, or password: those stay in the client config, and the agent only ever names the alias.

Point the same server at production with READ_ONLY=true and steps 2 through 4 simply do not exist — the write tools are never registered, so the agent cannot see them to call them.

Quick Start

Requires Node.js 18+. Register it with your MCP client — no install step:

{
  "mcpServers": {
    "db-gateway": {
      "command": "npx",
      "args": ["-y", "db-gateway"],
      "env": {
        "DBS": "mysql,redis",
        "MYSQL": "mysql://<user>:<password>@<host>:3306/<database>?alias=dev&default=true",
        "REDIS": "redis://:@<host>:6379/0?alias=dev&default=true"
      }
    }
  }
}

DBS decides which engines are enabled — only those tools get registered.

Connection strings

One string per engine. Semicolons separate multiple instances.

Variable	Format
MYSQL	mysql://<user>:<password>@<host>:<port>/<db>?alias=name
POSTGRESQL	postgresql://<user>:<password>@<host>:<port>/<db>?alias=name&ssl=true
REDIS	redis://:<password>@<host>:<port>/<db-index>?alias=name
MONGODB	mongodb://<user>:<password>@<host>:<port>/<db>?alias=name
REDSHIFT	redshift://<user>:<password>@<host>:<port>/<db>?alias=name&ssl=true
ELASTICSEARCH	elasticsearch://<user>:<password>@<host>:<port>?alias=name, or http(s)://<host>:<port>?alias=name
KAFKA	kafka://<user>:<password>@<broker>:<port>,<broker2>:<port>?alias=name&mechanism=plain

alias is required. It is how tools address a specific instance — omit it and that engine fails to connect.

Several instances of the same engine — separate their connection strings with a semicolon. The agent picks one by passing an alias argument to any tool; default=true marks the one used when no alias is given:

MYSQL="mysql://<user>:<password>@<dev-host>:3306/<db>?alias=dev&default=true;mysql://<user>:<password>@<prod-host>:3306/<db>?alias=prod"

DynamoDB is the exception — it takes DYNAMODB_REGION, DYNAMODB_ACCESS_KEY_ID, and DYNAMODB_SECRET_ACCESS_KEY instead. See .env.example for every option.

Read-Only Mode

READ_ONLY=true hides write tools from the tool list entirely and restricts *_execute_query to SELECT-style statements.

Register production as a second MCP server with this flag on. The agent then cannot modify production data — the write tools do not exist as far as it can see.

"db-gateway-prod": {
  "command": "npx",
  "args": ["-y", "db-gateway"],
  "env": { "READ_ONLY": "true", "DBS": "mysql", "MYSQL": "..." }
}

Documentation

• Tool Reference — all 145+ tools, by engine
• Connection Management — pooling, health checks, and why connectionLimit multiplies per session
• Deployment — SSE mode, Nginx, PM2, sharing one gateway across a team

License

MIT