n8n connects with a plain Nevermined API key, not the OAuth “approve a spending cap” flow that some assistants (Claude, ChatGPT) use. The key is your credential — it spends whatever its Nevermined account funds, so you set the budget on your account, not in n8n.
Before you connect
1
A Nevermined account
Free, at nevermined.app.
2
A Nevermined API key
Create a plain API key in the app — Settings → Global NVM API Keys — for the environment you want, and send the whole string, prefix included (
sandbox:… or live:…). A key minted by an OAuth flow can’t pay through the Router’s delegation routes, so use a plain one. See Get a Nevermined API key.3
A way to pay
The key spends from one of two budgets you set up once: a Nevermined Subscription whose monthly credits a plain key can spend, or a spending delegation — a capped, revocable budget funded from your own wallet (Using the Catalog from a harness walks through it). Discovery is free and needs neither.
Start on sandbox, where you use testnet funds and nothing costs real money, before you point n8n at live.
Add the Catalog to n8n
1
Add an MCP Client Tool node
In your workflow, add an MCP Client Tool node and connect it to your AI Agent node’s tool input.
2
Point it at the server
Set the endpoint to the Catalog MCP URL for your environment, and choose HTTP Streamable as the transport:
The Catalog MCP speaks Streamable HTTP only. If your n8n version offers only an SSE endpoint field, update n8n to a version with the HTTP Streamable transport option.
3
Set Bearer authentication
Set Authentication to Bearer and paste your Nevermined API key — or use a Header Auth credential with name
Authorization and value Bearer <your Nevermined API key>.Your Nevermined API key
That key is your credential — there is no separate consent screen to approve. Keep the prefix: alive: key for mcp.live, a sandbox: key for mcp.sandbox.
The key spends whatever its account funds — your Subscription credits, or a spending delegation funded from your wallet — so the budget and the audit trail live on your Nevermined account, not in n8n. Store it in an n8n credential, treat it like a password, and never commit it or paste it into a shared chat. Every way to mint one: Get a Nevermined API key.
Make your first paid call
Give your agent a task that needs a live, paid service, so it reaches for the Catalog tools rather than answering from memory.1
Browse for free
Have the AI Agent call a free discovery tool first — list the Nevermined catalog categories, or search the catalog for a weather service. Discovery needs no payment.
2
Let it buy
Then have it pay a service by slug — buy the service
<slug> and return the response. The paid call draws on your subscription credits or delegation and returns the merchant’s response.Disconnect or rotate the key
- Stop the credential (Nevermined side). The key is the credential, so to cut n8n off, rotate or delete the key in the app (Settings → Global NVM API Keys) — every call with the old key then fails. To cap spending without revoking the key, revoke the delegation it spends from in Payment methods; discovery still works.
- Remove the server (n8n side). Delete or disable the MCP Client Tool node in your workflow (and remove the stored credential if you no longer need it).
Next
Using the Catalog from a harness
The full plain-key playbook — discovery, delegations, and the safety rules.
Catalog MCP — full reference
Every tool, the API-key header, and every refusal code.