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Google Antigravity can browse the Nevermined Catalog and pay for services as it works, without you handing over an API key. You add one server, approve a single spending cap, and Google Antigravity does the rest. This is the per-host walkthrough; for the concept and the other assistants, see Using the Catalog from your web assistant.

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Before you connect

1

A Nevermined account

Free, at nevermined.app. You never share an API key with Google Antigravity — the consent cap is the credential.
2

A funded wallet

A paid call draws on a spending cap you approve during connect — a commerce grant: a capped, revocable budget funded from your own wallet, not a key. Fund that wallet first with the asset the service settles in — see Fund your wallet. You approve the cap itself in Approve the spending cap.
Start on sandbox, where you use testnet funds and nothing costs real money, before you point Google Antigravity at live.

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Add the Catalog to Google Antigravity

1

Add the server to Antigravity's MCP config

Open the raw MCP config — in the agent side panel, … → MCP Servers → Manage MCP Servers → View raw config (stored at ~/.gemini/config/mcp_config.json) — and add the Catalog as a remote server, using the serverUrl key (Antigravity does not accept url or httpUrl):
For live, use https://mcp.live.nevermined.app/mcp. Antigravity then runs an OAuth (PKCE) flow to authorize; depending on your build it may complete the flow on its own or ask for an OAuth client id / secret — we are confirming which (see the note below).
2

Authorize

When Antigravity prompts to authorize the server — use the Authenticate action next to it — it opens Nevermined’s consent page. See Approve the spending cap. (We are confirming at D4 whether Antigravity authorizes up front or on the first paid call — see the note below.)
Antigravity’s remote-MCP OAuth support is still settling across versions, and the config path differs between builds. We are validating the exact steps at D4 — including whether Antigravity authorizes up front or on the first paid call. If it only authorizes on connect, this page will switch to the mcp.api.<env> host, which challenges on connect instead. If authorization does not complete, confirm your Antigravity build supports remote MCP servers with OAuth.

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Approve the spending cap

Google Antigravity opens Nevermined’s consent page when it runs the OAuth flow to authorize the server. It is the one place a human is required.
1

Check who and where

The page shows the Sandbox / Live badge and who is asking. On live, the cap is real money.
2

Set the cap and validity

Set the spending cap (USDC or EURC) and how long the grant is valid for, then Grant access.
That approval is a commerce grant: it spends only from the budget you just approved, only through the Router, and you can revoke it any time. Nevermined’s routing fee comes out of the same cap, and the grant can also read your payment history and wallet balance — the cap bounds what it can spend, not what it can see.

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Make your first paid call

Ask for something only live data can answer, and name the connector so Google Antigravity reaches for it rather than answering from memory.
1

Browse for free

Ask “list the Nevermined catalog categories” — a free tool call, no sign-in.
2

Ask it to buy

“Buy the service with slug <slug> through the Nevermined connector and show me the response.” The paid call draws on the cap you approved and returns the merchant’s response.
If Google Antigravity answers without paying, it answered from its own knowledge — name the connector and ask for live data. More on phrasing: Catalog MCP tips.

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Disconnect

  • Revoke the budget (Nevermined side). Open Connections and disconnect Google Antigravity. The credential stops working on its next call; discovery still works.
  • Remove the connector (Google Antigravity side). Remove the Nevermined entry from Antigravity’s mcp_config.json.
To spend again — after you disconnect, or after a cap is used up — re-run the connect step and approve a new cap. A budget is never widened or extended in place.

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Next

Using the Catalog from your web assistant

The concept and the other assistants.

Catalog MCP — full reference

Every click path, the consent details, and every refusal code.