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Most Catalog services answer the paid call with what you bought. Some can’t: generating an image or a video, running a long scrape or placing a phone call takes longer than one request. Those services work in two steps:
  1. You pay to start the job. The service answers with a job id.
  2. You come back for the result with that id. This step is free, and only you can do it, because the result belongs to whoever paid.
The Router handles the second step for you. You don’t sign anything or manage keys: you call the result endpoint like any other, and the Router proves to the service that you’re the one who paid.

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Example

StableStudio generates images this way. Pay to start the job, then check on it with the id you got back.
Start the job with pay_service:
Then check on it, with the job id in the path. Set fresh: true every time you check, so each check is a new request:
The check comes back with paid: false, meaning nothing was charged:
Keep checking until the job is done. The endpoint’s description in the Catalog tells you what to look for, such as status becoming complete.

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How to spot these services

In the Catalog, the result endpoint is marked auth: "siwx", and its path has a placeholder for the id:
You see it in the service’s endpoints in the Catalog feed and in get_service. Any endpoint with auth: "siwx" is free, and only works after you’ve paid that same service.

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Three things to get right

  • Use the same service. Check through the same slug you paid.
  • Fill in the id. Replace {jobId} (or :id) with the id the paid call returned. A path that still has the placeholder is refused.
  • Pay from your own wallet. Only the wallet that paid can read the result. If the paid call would be funded by an organization wallet or a card, it’s refused before you’re charged, because nobody could collect the result. Use a crypto Delegation on your own wallet.
  • Subscription credits don’t pay these services, except a few reviewed endpoints whose paid response is already the whole result (no job to check back on, nothing you then own at the merchant). Everywhere else credits are refused with 403 BCK.SUBSCRIPTION_ROUTER.0001 with params.reason: "wallet_bound", and the catalog shows the price as own crypto wallet only.
Check back in time, too: the free check works for 1 hour after the paid call on Nevermined’s production deployments (the window is set per deployment), as long as that payment has settled by the time you check. After that hour, the check is refused.

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If it doesn’t work

The same code can have several causes, so read the error’s details to tell them apart.

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Under the hood

The service asks for proof in its own protocol, and the Router answers with your wallet’s signature: an MPP zero-amount proof or an x402 Sign-In-With-X. Neither one can move money. The guardrails list every check the Router makes before it signs.

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Next

Discover services

Find a service and read its endpoints.

How the Router works

The paid call, end to end.