What an MCP server does here
Model Context Protocol servers are how Antigravity reaches outside the workspace — a running process or remote endpoint that exposes tools the agent can call: GitHub operations, database queries, deployment APIs, ticket trackers. Inside Antigravity the contract is one JSON file: mcp_config.json in the workspace .agents/ directory, or the global ~/.gemini/antigravity/mcp_config.json for servers that follow you across projects.
The config is a map of server names to transport definitions — command + args for a local stdio process, serverUrl for a remote endpoint. That last detail is where most failed installs start.
The rules that actually bite
serverUrl, not url. Antigravity's config schema uses serverUrl for HTTP transports. Several MCP servers document url or httpUrl because those keys work in other clients — in Antigravity the server silently fails to register. Every entry here notes the exact key the server's own Antigravity guide uses.
Streamable HTTP only for remote. The legacy HTTP+SSE transport is not supported. A remote server that only speaks SSE needs a local bridge (typically npx mcp-remote as a stdio command) rather than a direct serverUrl entry.
Local stdio needs absolute paths. command resolves against the environment the app spawns, not your shell — relative paths, ~ and PATH-dependent shims are the top causes of a server that starts in the terminal and never appears in the panel.
Tokens belong in env or headers, not in the URL. Antigravity supports headers on remote entries for bearer auth; the entries here flag which servers expect a PAT, an OAuth flow, or an API key variable.
Plugins can ship MCP servers too. A plugin.json can bundle an MCP server alongside skills and agents — when you install a plugin, its servers register without a manual config entry. If a server exists both in a plugin and in your mcp_config.json, expect a name collision; the docs recommend the plugin path when the same vendor offers both.
How entries are verified
Each entry was checked against the server's own Antigravity (or generic MCP) install documentation — we record the config key it uses, the transport it needs, and anything in the install that does not survive copy-paste (absolute paths, profile flags, account setup). Servers without an Antigravity-specific guide are marked as such; a plain mcpServers entry usually works, but the gap is flagged rather than papered over.
Plugins can also ship MCP servers bundled inside a plugin.json manifest — see the plugins hub for that packaging path. For the underlying protocol reference, the official docs live at antigravity.google/docs/mcp.
The operational bar is the same as code: a server you cannot explain does not belong in the config.