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Best pay-per-call webhook ingress APIs for AI agents (September 2026)

Ranked by evidence from Zero's own probes and real agent calls · Updated Sep 29, 2026 · 12 agents searched Zero for this in the last 90 days

Zero indexes 6 pay-per-call services for webhook ingress. Of the 6 ranked here, 4 answered a live probe in the last 7 days. Quoted price is $0.002 per call, paid per call over x402 or MPP with no API key. The one with real agent usage in the last 30 days is Enable or Rotate Task Webhook Secret. The cheapest live option is Webhook Tester API at $0.002.

  1. scheduler.withzero.xyzEnable or Rotate Task Webhook Secret61

    Generates or rotates a one-time-shown webhook secret for a scheduled task, enabling walletless trigger authentication via Bearer token.

    Free/message

    Not verified recently2 calls · 30 days

  2. webhook-tester.api.klymax402.comWebhook Tester API5.0(1)4x402

    Sends a test HTTP request to a specified webhook URL and returns an analysis of the response

    $0.002000/message

    Live · checked Oct 1, 20260 calls · 30 days

  3. inbox.withzero.xyzRegister External Webhook Source (inbox.withzero.xyz)3

    Registers an external webhook source (GitHub, Stripe, or generic) and returns the inbound URL and HMAC secret to configure in the external system.

    Free/message

    Live · checked Oct 1, 20260 calls · 30 days

  4. gateway.spraay.appgateway.spraay.app Webhook Listx402

    Returns a list of all registered webhooks for the account on the Spraay gateway.

    $0.002/message

    Live · checked Sep 29, 20260 calls · 30 days

  5. inbox.withzero.xyzList Webhook Connections7mpp

    Returns all registered external webhook connections for your inbox, including their IDs, names, source types, inbound URLs, and creation timestamps.

    Free/message

    Live · checked Sep 30, 20260 calls · 30 days

  6. scheduler.withzero.xyzDisable Task Webhook1

    Deletes and clears the webhook secret for a scheduled task, disabling webhook delivery idempotently.

    Free/message

    Not verified recently0 calls · 30 days

Call one from an agent

zero fetch --capability scheduler-withzero-xyz-enable-or-rotate-task-webhook-secret-e257468a --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.