db-mcp

db-mcp is a Model Context Protocol (MCP) server that exposes database operations for HighGo (瀚高) and MySQL databases as MCP tools. AI assistants such as OpenCode and Claude Code can query, modify, and inspect databases through a permission-controlled, stdio-based interface.

Features

• Two database types: HighGo (PostgreSQL-compatible) and MySQL, selected via configuration

• Five MCP tools: query, execute, DDL, list tables, and describe table

• Fine-grained permissions: per-operation allowlist (SELECT / INSERT / UPDATE / DELETE / DDL)

• Flexible configuration: environment variables or a JSON config file (env vars take precedence), with ${ENV_VAR} placeholder support in config files

• Connection pooling: configurable pool size per connection

• Single-file build: build:prod bundles everything into one self-contained dist/index.js — no node_modules needed at runtime

Related MCP server: Multi-DB MCP Server

Requirements

• Node.js >= 18

Quick Start

npm install
npm run build:prod

npm run build:prod runs tsc and then bundles the output with esbuild into a single file:

dist/
└── index.js    # self-contained, run directly with node

Note: npm run build (tsc only) also compiles to dist/, but that output still requires node_modules/ at runtime. Use build:prod for a portable single-file build.

Run the server (it speaks MCP over stdio, so it is normally launched by an MCP client, not run interactively):

node dist/index.js

Configuration

Two ways to configure a connection; environment variables take precedence over the config file.

Option 1: Environment variables

DB_HOST=127.0.0.1 DB_PORT=5866 DB_DATABASE=mydb DB_USERNAME=admin DB_PASSWORD=xxx node dist/index.js

Option 2: Config file

The server loads ./db-mcp-config.mysql.example.json from the current working directory by default. Copy one of the examples from config/ and point DB_MCP_CONFIG at it:

# e.g. on Windows
set DB_MCP_CONFIG=D:\path\to\db-mcp\config\db-mcp-config.highgo.example.json
node dist/index.js

Or place a config file named db-mcp-config.mysql.example.json in the working directory (the default path).

Example config:

{
  "name": "highgo-dev",
  "type": "highgo",
  "host": "127.0.0.1",
  "port": 5866,
  "database": "your_database",
  "username": "your_username",
  "password": "your_password",
  "pool": { "max": 10 },
  "permissions": ["SELECT", "INSERT", "UPDATE", "DELETE", "DDL"]
}

Config file fields: name, type (highgo | mysql), host, port, database, username, password, pool.max, permissions. Values may reference environment variables with ${ENV_VAR} syntax, e.g. "password": "${DB_PASSWORD}".

⚠️ The config file contains database credentials — never commit real values to git. The shipped examples under config/ only contain placeholders.

Connecting an MCP Client

OpenCode

Add the server to the mcp field of opencode.json (project root) or your global config:

Via environment variables:

{
  "$schema": "https://opencode.ai/config.json",
  "mcp": {
    "db-mcp": {
      "type": "local",
      "command": ["node", "/path/to/db-mcp/dist/index.js"],
      "enabled": true,
      "environment": {
        "DB_TYPE": "highgo",
        "DB_HOST": "127.0.0.1",
        "DB_PORT": "5866",
        "DB_DATABASE": "your_database",
        "DB_USERNAME": "your_username",
        "DB_PASSWORD": "your_password",
        "DB_PERMISSIONS": "SELECT,INSERT,UPDATE,DELETE,DDL"
      }
    }
  }
}

Via config file:

{
  "$schema": "https://opencode.ai/config.json",
  "mcp": {
    "db-mcp": {
      "type": "local",
      "command": ["node", "/path/to/db-mcp/dist/index.js"],
      "enabled": true,
      "environment": {
        "DB_MCP_CONFIG": "/path/to/db-mcp/config/db-mcp-config.mysql.example.json"
      }
    }
  }
}

Or add it interactively with the CLI:

opencode mcp add

OpenCode walks you through the setup step by step:

1. Run opencode mcp add — an interactive prompt opens.

2. Select local as the server type.

3. Give the server a name, e.g. db-mcp.

4. Enter the command: node /path/to/db-mcp/dist/index.js.

5. Add the environment variables when prompted (DB_TYPE, DB_HOST, ... or DB_MCP_CONFIG).

6. Verify the server is connected with opencode mcp list.

If the server is slow to start up, raise the tool-fetch timeout with "timeout": 10000 (defaults to 5000 ms).

Codex

MCP servers are configured in ~/.codex/config.toml under the [mcp_servers] section. Add the server with the Codex CLI:

codex mcp add db-mcp --env DB_MCP_CONFIG=/path/to/db-mcp/config/db-mcp-config.mysql.example.json -- node /path/to/db-mcp/dist/index.js

Or edit ~/.codex/config.toml directly:

[mcp_servers.db-mcp]
command = "node"
args = ["/path/to/db-mcp/dist/index.js"]
enabled = true

[mcp_servers.db-mcp.env]
DB_MCP_CONFIG = "/path/to/db-mcp/config/db-mcp-config.mysql.example.json"

To connect via environment variables instead, list them in the env table (see Option 1).

Claude Code

Add the server with the Claude Code CLI (saved to ~/.claude/settings.json by default; pass --scope project to save it to .mcp.json in the project root instead):

claude mcp add -e DB_MCP_CONFIG=/path/to/db-mcp/config/db-mcp-config.mysql.example.json db-mcp -- node /path/to/db-mcp/dist/index.js

Or edit .mcp.json (project scope) or ~/.claude/settings.json (user scope) directly:

{
  "mcpServers": {
    "db-mcp": {
      "type": "stdio",
      "command": "node",
      "args": ["/path/to/db-mcp/dist/index.js"],
      "env": {
        "DB_MCP_CONFIG": "/path/to/db-mcp/config/db-mcp-config.mysql.example.json"
      }
    }
  }
}

Tools

Permission Control

Every connection carries a permissions allowlist. Requests are rejected with an error when the required permission is missing:

• db_query / db_list_tables / db_describe_table require SELECT

• db_execute checks the statement prefix and requires INSERT, UPDATE, or DELETE accordingly

• db_ddl requires DDL

To restrict a connection, set DB_PERMISSIONS (comma-separated) or the permissions array in the config file. Restrictive example: SELECT,DDL allows reads and schema changes but no DML writes.

Project Structure

src/
├── index.ts                    # MCP server entry: tool registration + stdio transport
├── config.ts                   # config loading, permission checks, SQL validation
├── types.ts                    # shared types (ConnectionConfig, QueryResult, ...)
└── clients/
    ├── highgo-client.ts        # HighGo client implementation
    └── mysql-client.ts         # MySQL client implementation
config/
├── db-mcp-config.highgo.example.json
└── db-mcp-config.mysql.example.json
highgodb/                       # vendored HighGo database driver (based on pg), installed via file: dependency

Development

npm install
npm run dev        # watch mode via tsx (src/index.ts)
npm run build      # tsc compile only
npm run build:prod # tsc + esbuild single-file bundle

Security Notes

• The server executes arbitrary SQL within the granted permissions — run it with the least-privileged database account your use case allows.

• The MCP transport is stdio and does not enforce authentication on its own; control access to the machine/process that hosts it.

• Read-only tools are marked with readOnlyHint so clients can route them accordingly, but enforcement happens through the permission allowlist.

• Keep credentials out of version control (see the config section).

License

MIT