For the complete documentation index, see llms.txt

Kapa MCP server

The Kapa MCP server exposes the same Midnight knowledge base that powers the "Ask AI" button on this documentation site. It gives your AI coding assistant documentation-grounded answers about Midnight directly in your editor, so you can ask questions without switching to a browser tab.

For background on why the project moved to Kapa and how it fits alongside Midnight Expert, see the migration blog post.

Install

The server URL is https://midnight.mcp.kapa.ai. After you add it to a client, sign in so your assistant can use the server.

Claude Code

Run this command in your terminal, not inside a Claude Code session:

claude mcp add --transport http midnight https://midnight.mcp.kapa.ai

Claude Code registers the server for the project where you run the command. Start Claude Code in the same folder, run /mcp, select midnight, and choose Authenticate to sign in.

To use the server in every project, add it with the --scope user option instead:

claude mcp add --scope user --transport http midnight https://midnight.mcp.kapa.ai

Claude on the web and desktop

To use the server from claude.ai in your browser or from the Claude desktop app, add it as a custom connector:

1. In Claude, open Customize > Connectors and select Add custom connector.
2. Enter a name and the server URL https://midnight.mcp.kapa.ai, then select Add.
3. Sign in when Claude prompts you. If the connector shows Connect, select it to start the sign-in.
4. In a chat, select +, then Connectors, and check that the connector is on.

On Team and Enterprise plans, an Owner adds the connector for the organization before members can connect. For the steps on each plan, see Add a connector by URL in the Claude documentation.

Codex

Run this command in your terminal:

codex mcp add midnight --url https://midnight.mcp.kapa.ai

Codex saves the server to ~/.codex/config.toml and starts the sign-in in your browser. The saved entry looks like this:

[mcp_servers.midnight]
url = "https://midnight.mcp.kapa.ai"

To sign in later, run codex mcp login midnight.

OpenCode

Add the server to the mcp section of your opencode.json file. Use the file in your project root, or ~/.config/opencode/opencode.json to make the server available in every project:

{
  "$schema": "https://opencode.ai/config.json",
  "mcp": {
    "midnight": {
      "type": "remote",
      "url": "https://midnight.mcp.kapa.ai"
    }
  }
}

Then sign in from your terminal. If you added the server to a project file, run the command from that project folder:

opencode mcp auth midnight

Cursor and VS Code

Open the "Ask AI" button on this site, click "Use MCP", and choose "Add to Cursor" or "Add to VS Code". Both are one-click installs.

Any other MCP client

For any client that supports remote MCP servers in a JSON config, add the server manually:

{
  "mcpServers": {
    "midnight": {
      "type": "http",
      "url": "https://midnight.mcp.kapa.ai"
    }
  }
}

Some clients label this a remote or HTTP server and ask for a transport field; the URL is the same in every case. You can also click "Copy MCP URL" from the "Use MCP" menu and paste it wherever your client expects it.

Field names differ between clients. Antigravity, for example, reads serverUrl instead of url. Its config file is ~/.gemini/config/mcp_config.json, or .agents/mcp_config.json in your project folder:

{
  "mcpServers": {
    "midnight": {
      "serverUrl": "https://midnight.mcp.kapa.ai"
    }
  }
}

Authentication

The server requires you to sign in before it answers. Until you do, it rejects requests with an HTTP 401 response, and your client reports that the server needs authentication. That message means the install worked and the server is waiting for you to sign in.

When you sign in, your client opens a Kapa page on mcp.kapa.ai in your browser, where you verify with a Google or GitHub account. The server doesn't use API keys. According to Kapa's documentation, the sign-in exists only to apply per-user rate limits and block abuse. Kapa uses only an opaque user ID from Google or GitHub. With Google it requests only the openid scope, so it doesn't see your name or email address. Your client stores the resulting token and reuses it in later sessions.

Each client reports the missing sign-in in its own way:

Client	What it reports	How to sign in
Claude Code	! Needs authentication in claude mcp list	In a session, run /mcp, select midnight, and choose Authenticate. In a terminal, run claude mcp login midnight from the folder where you added the server.
Codex	Not logged in in codex mcp list	Run codex mcp login midnight.
OpenCode	MCP Authentication Required, followed by Server "midnight" requires authentication. Run: opencode mcp auth midnight	Run opencode mcp auth midnight.

If you gave the server a different name, use that name in place of midnight. The Use MCP menu on this site names it midnight-docs.

Cursor, VS Code, and Antigravity also support this sign-in. Start it from the prompt the client shows or from its MCP settings.

What it covers

Kapa indexes a curated set of Midnight sources: the official documentation, hand-picked core repositories (the ledger, midnight.js, and the node), and standalone material such as the whitepaper. Ask how DUST generation works, how to structure a witness, or what a specific ledger type does, and you get an answer grounded in current documentation rather than stale training data.

Midnight Expert

For hands-on development tasks like writing and validating Compact contracts, running a local devnet, or decoding error codes, use Midnight Expert alongside Kapa. That page has the setup instructions, and the migration blog post explains how the two tools fit together.

Midnight Expert is a suite of Claude Code plugins. Its documentation has no setup for Codex, OpenCode, or other assistants, so connect the Kapa MCP server in those tools instead.