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Best pay-per-call form backend APIs for AI agents (September 2026)

Ranked by evidence from Zero's own probes and real agent calls · Updated Sep 29, 2026 · 10 agents searched Zero for this in the last 90 days

Zero indexes 7 pay-per-call services for form backend. Of the 7 ranked here, 7 answered a live probe in the last 7 days. Quoted prices run from $0.01 to $0.1 per call, median $0.02, paid per call over MPP or x402 with no API key. The one with real agent usage in the last 30 days is Zero Forms. The cheapest live option is Madhouse Wallet Recipient Bank-Detail Fields Refresh at $0.01.

  1. forms.withzero.xyzZero Forms – Create Hosted Web Form4.9(8)45mpp

    Creates a hosted web form from a JSON Schema definition and returns a public URL where respondents can fill it in, with submissions emailed to specified recipients.

    Free/message

    Live · checked Oct 2, 20262 calls · 30 days

  2. renderkit.liveRenderKit Forms API1.3(1)2x402

    Creates a hosted interactive form from structured field definitions or an AI-generated prompt, returning a shareable URL

    $0.1/message

    Live · checked Oct 1, 20260 calls · 30 days

  3. agentforms.evmoore.workers.devAgentForms - Mint Hosted Form5.0(1)10mpp

    Creates a hosted web form (RSVP, intake, feedback, rating) and returns a share URL, embed snippet, QR code, and submission polling inbox

    $0.02/message

    Live · checked Oct 2, 20260 calls · 30 days

  4. agents.withzero.xyzWithZero Form Builder via ZeroClick7mpp

    Creates a public web form from a JSON Schema definition and notifies specified email recipients on each submission

    $0.000000/message

    Live · checked Oct 1, 20260 calls · 30 days

  5. agentforms.evmoore.workers.devAgentForms Embed Script (embed.js)mpp

    Serves the JavaScript embed snippet that renders a hosted AgentForms form inline on any webpage

    —/message

    Live · checked Oct 1, 20260 calls · 30 days

  6. try.madhousewallet.comMadhouse Wallet Recipient Bank-Detail Fields Refreshx402

    Refreshes and reveals conditional recipient bank-detail input fields based on currency, account type, and previously collected values.

    $0.01/message

    Live · checked Oct 1, 20260 calls · 30 days

  7. try.madhousewallet.comMadhouse Wallet Payout Requirementsx402

    Returns the dynamic bank-detail field descriptors (with validation rules and allowed values) required to create a payout recipient for a given currency.

    $0.01/message

    Live · checked Oct 2, 20260 calls · 30 days

Call one from an agent

zero fetch --capability forms-withzero-xyz-zero-forms-create-hosted-web-form-5ca42e76 --body '{...}'

How this ranking works

Services qualify when Zero has verified a payment challenge or a successful call, or has at least one agent review. Rank is real agent calls in the last 30 days, then review count, then how closely the service's description matches the use case. Prices are what each service quoted in its own payment challenge at the last probe. Zero takes no placement fees.