Wire NCI into Antigravity

Locate mcp_config.json

Antigravity reads MCP servers from a single user-scoped file:

Launch Antigravity at least once so the ~/.gemini/antigravity/ directory exists, then create or open mcp_config.json.

Drop in the entry

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

That is the whole entry. nci-mcp walks the agent’s working directory the same way the CLI does, so opening a repo in Antigravity is enough — there is no NCI_PROJECT_ROOT env var.

When you need NCI_BINARY

If nci isn’t on Antigravity’s PATH, point at the binary explicitly:

{
  "mcpServers": {
    "nci": {
      "command": "npx",
      "args": ["-y", "@nativecontextindex/mcp"],
      "env": {
        "NCI_BINARY": "/absolute/path/to/nci"
      }
    }
  }
}

Find the absolute path with:

Reload the agent

Antigravity watches mcp_config.json and rebuilds the server list when it changes — no IDE restart needed. After saving the file, open the Agent panel and either end the current agent session and start a new one, or use the … menu and pick …MCP Servers to refresh. nci should show up with two tools and three resources.

If the refresh button doesn’t pick up the change (rare — usually only on stale binaries), use the command palette and run Developer: Reload Window. A full Antigravity restart is almost never necessary.

First call

The agent should read nci://primer/agent first — that resource is the operating manual the MCP server’s instructions field tells it to load. Then ask:

List the public exports of zod’s installed version so we can wire a schema.

Gemini routes to nci_query with subcommand: "evidence" (or symbols if it wants the package surface) and quotes signatures back verbatim. Pin package_name and package_version in the prompt when you want exact answers fast — see the agent primer for why.

Troubleshooting

• The Agent panel shows nci but tool calls fail → run nci binary-path, set NCI_BINARY to that path in the env block, then refresh from …MCP Servers.
• “Tool unavailable” on first message → the repo wasn’t indexed yet. Open a terminal in Antigravity, run nci index, retry.
• Two MCP entries collide on the name nci → rename one (e.g. nci-monorepo); Antigravity dedupes by key, not by command.

Skills

Antigravity follows the open Agent Skills standard. NCI’s shipped skill (nci-answer-quality) drops into Antigravity’s discovery path with no rewriting — see NCI Skills for the host-by-host map.