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Codex 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 Codex 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 Codex — 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 Codex at live.

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Add the Catalog to Codex

1

Add the server to your Codex config

Add an MCP server entry to ~/.codex/config.toml (or a project-scoped .codex/config.toml) pointing at the environment you want. Codex reaches remote servers over Streamable HTTP:
Leave any client id / secret out — Codex identifies itself to Nevermined with its own client metadata document and runs the OAuth (PKCE) flow, so there is nothing to register and no key to paste.
2

Sign in

Run codex mcp login nevermined. Codex opens Nevermined’s consent page in your browser — see Approve the spending cap.

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Approve the spending cap

Codex opens Nevermined’s consent page when you run codex mcp login. 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 Codex 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 Codex 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 Codex. The credential stops working on its next call; discovery still works.
  • Remove the connector (Codex side). Run codex mcp logout nevermined first to clear the stored OAuth tokens, then remove the [mcp_servers.nevermined] block from your config.toml (or run codex mcp remove nevermined). To keep the entry but switch it off instead, set enabled = false.
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.