Where does Antigravity keep mcp_config.json, and why does your edit sometimes change nothing? See the global and workspace paths on Windows, macOS and Linux, the three ways to open the file, how the MCP Store adds servers, a working JSON example, and fixes for the errors people hit most.
You paste a new server into Antigravity, press Refresh, and the tool list stays empty. Often the server is fine. The problem is the file: which mcp_config.json the app reads, where it sits on your disk, and whether the JSON uses the field names Antigravity expects. Google's own pages point to two different paths, forum posts show people editing the wrong copy, and the error messages are short enough to feel like riddles.
This article pins down the facts. You get the exact file location on Windows, macOS and Linux, three ways to open the file from the app, a tour of the MCP Store, a config that holds up, and a plain fix for each common error. Where the sources disagree, the text says so instead of guessing.
Antigravity keeps every MCP server definition in one JSON file named mcp_config.json. The official MCP page lists a global file that applies to all projects and a workspace file that applies to a single repository.
| System | Global path |
|---|---|
| Windows | %USERPROFILE%\.gemini\config\mcp_config.json |
| macOS | ~/.gemini/config/mcp_config.json |
| Linux | ~/.gemini/config/mcp_config.json |
On Windows, %USERPROFILE% expands to something like C:\Users\YourName. The .gemini folder starts with a dot, so Finder and most Linux file managers hide it. In Finder press Cmd+Shift+. to show hidden items, in the Windows file manager tick Hidden items under the View menu, or skip the browsing and paste the full path into the address bar or the Go to Folder box.
Inside a repository, the docs name .agents/mcp_config.json as the workspace location. It suits servers that only make sense for one codebase, such as a database server pointed at that project's development schema. A Japanese troubleshooting write-up reports that workspace settings can override the global file, so check this path first when a server behaves differently inside one repo.
💡 Tip: If a workspace file holds tokens, add
.agents/mcp_config.jsonto.gitignorebefore your next commit.
The current docs and the CloudBees Unify setup page use ~/.gemini/config/mcp_config.json. Older tutorials, many server READMEs and the macOS PATH bug report use ~/.gemini/antigravity/mcp_config.json. The OAuth token file also sits in the antigravity folder, which is part of why that folder name keeps showing up.
No page says which file wins when both exist. Settle it with a test: add a harmless entry to one file, press Refresh, and see whether it appears in the server list. If it does not, you edited the wrong one. Then keep a single live file and rename the stray copy to mcp_config.json.bak so the two never drift apart. Opening the file through View raw config in the IDE is the quickest way to see which one your build uses.
You do not have to hunt through hidden folders. Each Antigravity surface has its own door to the same configuration.
In the Antigravity IDE, click the … menu at the top of the agent side panel, then choose MCP Servers, then Manage MCP Servers, then View raw config. The file opens in the editor. Save it, go back to the Manage MCP Servers screen and press Refresh. That last click is the step the troubleshooting threads recommend again and again.
In Antigravity 2.0 the route is Settings (bottom left), then Customizations, then Installed MCP Servers. Each server has a toggle, a trash can and a shared Refresh button. The command line tool has its own door: type /mcp in the prompt panel to open the interactive MCP Manager. It also shows connection logs, including response codes such as 401, 403 and 404 and timeouts, which makes it the best place to read what actually went wrong.
The MCP Store is a searchable list of ready-made servers. The docs describe 76 or more integrations across databases, developer tools, design platforms, security and analytics. You reach it from Installed MCP Servers by clicking Add MCP, or from the MCP Servers menu in the IDE agent panel.
Open the raw config once after your first store install. The entry the store wrote is a ready-made template for the entries you write by hand later.
💡 Tip: Use the store for servers that need OAuth, because it handles the sign in screen. Use hand-written JSON for local scripts, private servers and anything that needs custom headers.
Per the docs, OAuth tokens are saved in ~/.gemini/antigravity/mcp_oauth_tokens.json. Treat that file like a password vault: keep it out of dotfile repositories and cloud sync folders. When a sign in keeps failing, use the Sign out button in the IDE first, or check for the Authed status in the CLI /mcp view. Deleting the token file is a last resort, and it may sign you out of every remote server at once.
The file has one top-level object, mcpServers, and every server is a named entry inside it. Names should have no spaces. A forum thread about the Figma server found that a suggested name like "Figma Desktop" had to become FigmaDesktop, and that the URL field had to be serverUrl, not url.
{
"mcpServers": {
"filesystem": {
"command": "npx",
"args": ["-y", "@modelcontextprotocol/server-filesystem", "C:/Users/you/projects"],
"env": { "NODE_ENV": "production" },
"cwd": "C:/Users/you/projects"
}
}
}
On Windows, write paths with forward slashes or double the backslashes (C:\\Users\\you), because a single backslash is an escape character in JSON. Here is what each field does:
| Field | Purpose | Notes |
|---|---|---|
command | Program that starts a local server | Must be on PATH, or use an absolute path |
args | Arguments for that program | One string per argument |
env | Environment variables | Put tokens here instead of in args |
cwd | Working directory | Optional |
serverUrl | Endpoint of a remote server | Replaces command for HTTP servers |
headers | HTTP headers sent to a remote server | Bearer tokens go here |
oauth | Client settings such as clientId | Needed by some remote servers |
disabledTools | Tool names hidden from the model | Helps with the 100 tool limit |
{
"mcpServers": {
"remote-example": {
"serverUrl": "https://api.example.com/mcp/",
"headers": { "Authorization": "Bearer YOUR_TOKEN" }
}
}
}
The docs say plain url fields are not supported for remote servers, so a snippet copied from another editor needs that one rename. Servers that use OAuth take an oauth block instead of a header: the CloudBees page shows "oauth": { "clientId": "public-mcp-client" }. For Google Workspace servers you create a Web application OAuth client in Google Cloud Console, add https://antigravity.google/oauth-callback as a redirect URI, and put the clientId and clientSecret in the oauth section. Servers that accept Google application default credentials use "authProviderType": "google_credentials".
Before saving, check three things that break JSON more often than any Antigravity bug: trailing commas, comments (JSON allows none), and curly quotes pasted from a web page.
| Message | Likely cause | First fix |
|---|---|---|
context deadline exceeded or [MCP Proxy] Socket connection error: connect ENOENT | Initialization failed at IDE startup | Manage MCP Servers, then Refresh |
exec: "npx": executable file not found in $PATH | The app launched from the Dock or Spotlight without your shell PATH | Launch with agy from a terminal, or use an absolute path |
calling 'initialize': sending 'initialize': Unauthorized | Token missing from the first request to a remote server | Update the app and sign in again |
enabled tools would exceed max limit of 100 | Too many enabled tools across all servers | Disable servers or list disabledTools |
connection closed: calling 'initialize': client is closing: EOF | The server process exited during the handshake | Run the same command in a terminal and read its output |
This shows up at startup, together with the ENOENT socket message, when a server does not finish initializing in time. The reported fix is simple: open Manage MCP Servers and press Refresh. If it comes back at every restart, a practical workaround is to install the server package globally and point command at the installed binary, so nothing has to be downloaded while the IDE is booting.
Messages such as exec: "npx": executable file not found in $PATH appear when Antigravity is started from the macOS Dock or Spotlight. The app inherits the sparse system PATH (/usr/bin:/bin:/usr/sbin:/sbin) instead of the one from your shell profile. The thread reports it on version 1.22.2 and lists these workarounds:
agy command.command. Run which npx and paste the result, for example /opt/homebrew/bin/npx on a typical Apple Silicon Homebrew setup.Windows users should run where npx in a terminal first. If it prints nothing, the problem is the Node install, not the config.
An Unauthorized error on initialize means a remote server got the first request without a usable token. Update Antigravity, sign out of the server and sign in again. If you use a header token, confirm the field is named Authorization, the value starts with Bearer and the token has not expired. The status code in the CLI /mcp logs narrows it down: 401 points to missing or bad credentials, 403 to a token without the right permissions, and 404 to a wrong URL path.
Antigravity refuses to connect when the enabled tools across all servers would pass 100. Large servers for GitHub or databases can expose dozens of tools each, so three or four of them are enough to hit the wall. Switch off servers you are not using, or hide individual tools with the disabledTools property listed in the docs.
One more pattern is worth knowing. A report on the Google AI developers forum describes a Roblox Studio server, started through a batch file, that failed with the EOF message on Hub 2.4.3, 2.5.0 and 2.8.0 and only worked again after rolling back to Hub 2.2.1. When a local server fails this way, run its exact command in a terminal. If it fails there too, the config is fine and the server is the problem. If it works there, suspect a version regression and check the forum before changing your JSON.
When the JSON refuses to behave, a language model makes a fast proofreader. Gemini 3.1 Pro runs in the browser on PicassoIA, accepts text plus up to 10 images, and lets you set how hard it thinks before answering.
YOUR_TOKEN before pasting anything.high. Keep it for a long config with many servers. low is enough for a plain syntax check.The model cannot see your disk, so treat any path it suggests as a guess and check it against the table earlier in this article. For a second opinion on the same prompt, run it through Claude Sonnet 4.6 as well and compare the two answers.
Run through this list before blaming the server:
serverUrl, and local servers use command with args.command holds an absolute path.env or headers, and the file is out of version control if it holds secrets./mcp view.💡 Tip: A server that works in your terminal but fails inside Antigravity usually points to an environment difference, most often PATH. Compare
whichorwhereoutput with what the app sees.
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