# 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:

```bash
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`):

```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](https://github.com/questdb/mcp-server-questdb/releases):
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:

```bash
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/mcp-server-questdb@0.3.0 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:

```bash
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.