Can an AI agent generate images without an account or API key?

The agent posts the tool name and arguments. Because no payment is attached, the server answers 402 with payment requirements: the exact amount for those specific arguments, the asset, the network and the recipient. The agent signs a payment authorisation, repeats the same request with an X-PAYMENT header, and receives the result.

Pricing is per call and argument-dependent, which is why the quote comes from a real request rather than a price list. The discovery manifest publishes the *minimum* price of each tool on purpose: it is there for indexers to find the service, not for an agent to sign a payment against, and advertising a maximum would make every cheap call look expensive.

One deliberate quirk: an empty or malformed POST also answers 402 rather than 400. That is what an indexer's probe looks like, and it decides whether the service is payable from the status code alone.

For images and speech, nothing — because settlement is two-phase. The signature is verified, the generation runs, and the transfer only executes once the file exists. A failure, a timeout or a content-filter rejection never takes the money.

Video cannot work that way. A running generation cannot be cancelled upstream, and no HTTP request can be held open for ten minutes, so video settles up front and returns a job id polled on a free result endpoint. If that job fails, the endpoint issues a refund token for the full amount, valid 90 days and redeemable against a later call; if the next call is cheaper, the remainder comes back as a new token. On-chain reversal is not an option — no private key sits on this server, and none should.

Use x402 when the agent is autonomous and holds funds: no human is available to sign a consent screen, and a wallet is easier to provision than an account. It also suits one-off or bursty workloads where a prepaid balance would just sit idle.

Use MCP when there is a person behind the agent. OAuth or an API key gives you generation history, a usage log per key, optional daily spend caps, video editing on clips you already own, and top-up bonuses. Two conversational tools — editing a video you generated earlier, and refining from a previous generation id — are MCP-only, because they operate on media that belongs to an account.