QuestDB MCP Server

An MCP server that connects coding agents (Claude Code, Codex, Cursor, OpenCode, Gemini CLI) to a running QuestDB Web Console. The agent gets tools to create notebook cells, run queries, and build charts. Every action executes in the browser against your already-established QuestDB session.

Setup

Quick setup (recommended)

The interactive wizard detects your installed coding agents and writes the bridge into each one's MCP config:

npx @questdb/mcp-server-questdb setup

It walks you through two steps:

1. Pick agents: multi-select from the ones it detects (Claude Code, Codex, Cursor, OpenCode, Gemini CLI).
2. Review settings: optionally override CONSOLE_ORIGIN and MCP_BRIDGE_PORT; press Enter to keep the defaults.

The wizard pins each agent's config to the bridge version that ran it. Your QuestDB Web Console expects a specific bridge version. If you're on an older console, run the matching version: npx @questdb/mcp-server-questdb@<version> setup. The config it writes will launch that same version. (When unsure, pair first; on a version mismatch the agent is told which version to switch to.) For versions earlier than 0.3.0, use the former package name instead: npx @questdb/mcp-bridge@<version> setup.

Manual setup

Or add it to your MCP client's config by hand (e.g. ~/.claude/.mcp.json):

{
  "mcpServers": {
    "questdb": {
      "command": "npx",
      "args": ["-y", "@questdb/mcp-server-questdb"]
    }
  }
}

Offline / restricted install (no npx)

Environments that can't run npx (no npm registry access, vet-then-vendor policies) can use the standalone bundle attached to each supported version's GitHub Release: a single self-contained .mjs file needing only Node ≥ 22, making no network connections except the local WebSocket to your Web Console.

Standalone bundles are available starting with bridge version 0.4.0. All supported QuestDB Web Console versions request bridge version 0.4.0 or later.

Download the bundle (mcp-server-questdb-<version>.mjs) and THIRD_PARTY_NOTICES.txt from the release, then move the bundle to a permanent location before setup—do not configure it from a downloads or temporary directory—and invoke that exact path:

node /permanent/absolute/path/mcp-server-questdb-<version>.mjs setup

Setup writes agent configs that launch the bundle file directly (no npx involved), so moving or deleting that exact path will prevent the MCP server from starting. To switch versions, put the matching bundle beside the current one and run node /permanent/absolute/path/mcp-server-questdb-<new-version>.mjs upgrade; it re-points your agent configs at the new file while keeping env settings. If a configured file was already moved, run upgrade from its new absolute path. setup and upgrade always write the install style of the binary you run: a bundle writes file-path configs; npx writes npx configs.

Environment variables

| Label | Value | Default Value | Description | | ----------------- | ----------------------------------- | -------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | CONSOLE_ORIGIN | origin URL | http://127.0.0.1:9000 | QuestDB Web Console origin. 127.0.0.1 and localhost are interchangeable. | | MCP_BRIDGE_PORT | 1–65535 | auto-allocated | When specified, the bridge uses a fixed port. The port is bound on the first pairing attempt, pairing fails with a bridge_bind_failed error if the port is taken. | | LOG_PATH | file path | /tmp/questdb-mcp-bridge/<ISO-ts>-<pid>.log | Override the log file location. | | LOG_LEVEL | ERROR / WARN / INFO / DEBUG | INFO | DEBUG adds heartbeats and full tool payloads. |

Commands

Your MCP client runs the bridge for you via the config above, so you rarely invoke it by hand. When you do:

| Command | Description | | ------------------------------------------- | ---------------------------------------------------------- | | npx @questdb/mcp-server-questdb (no args) | Start the bridge — same as start. | | npx @questdb/mcp-server-questdb start | Start the bridge. | | npx @questdb/mcp-server-questdb setup | Interactively configure the bridge for your coding agents. | | npx @questdb/mcp-server-questdb --version | Print the version and exit. Alias: -v. | | npx @questdb/mcp-server-questdb --help | Print this help and exit. Alias: -h. |

An unknown command exits non-zero with a short error. Pin a version with npx @questdb/[email protected] start. (Installed on your PATH, the executable is named mcp-server-questdb.)

Pairing

Before any notebook / chart / SQL tool works, your browser has to pair with the bridge. The agent drives the flow.

When the agent needs to pair, it calls get_pairing_credentials and shows you both:

• A one-click deep link — open it in the tab showing your Web Console.
• A WebSocket URL + token — paste into the MCP pill at the bottom of the Web Console if the deep link doesn't land in the right tab.

Either path lands you on a consent prompt. Accept it and the agent's next tool call goes through.

Each bridge run generates a fresh port and pairing token, held only in memory. On restart the old credentials stop working — the agent will surface new ones the next time it needs to pair.

Logs

The bridge writes to stderr and to a log file. Tail the newest:

tail -F "$(ls -t /tmp/questdb-mcp-bridge/*.log | head -1)"

At default INFO:

2026-05-15T12:29:27.142Z [INFO] tool_call: run_query
2026-05-15T12:29:27.318Z [INFO] tool_result: run_query ok
2026-05-15T12:29:28.011Z [ERROR] tool_result: update_cell internal_error timeout after 15000ms

At DEBUG (full payloads as continuation lines):

2026-05-15T12:29:27.142Z [INFO] tool_call: run_query
2026-05-15T12:29:27.142Z [DEBUG]   args: {"query":"SELECT count() FROM trades"}
2026-05-15T12:29:27.318Z [INFO] tool_result: run_query ok
2026-05-15T12:29:27.318Z [DEBUG]   content: [{"type":"text","text":"..."}]

License

Apache-2.0.