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Head to head · Sending webhooks · October 2026 research run

402cron vs Ably

Ably scores 75.2 (BB) on agent readiness against 402cron's 63.5 (B), and leads in 5 of 7 scored categories. 402cron leads on payments & pricing. Both do sending webhooks. 402cron accepts x402. Ably doesn't.

Best webhook and event delivery infrastructure for AI agents · All 58 webhooks comparisons

402cronGeorgi Kalchev · HTTP API B63.5/100#452 of 1226 AblyAbly Realtime Ltd · HTTP API BB75.2/100#61 of 1226

Which one, for what

402cron B

Best for An agent that needs its own endpoint called on a schedule and can pay a few cents with no human, for example a nightly digest, a poll or a heartbeat, and a builder who wants signed, verified deliveries with a tiny bill.

Ahead on

  • Payments & pricing, 86 against 40

Also in its favour

  • An agent can pay per call over x402, with no account

Watch for

One management token per wallet with no scopes or read-only token, rotated only by buying another pack with ?rotate=1

Ably BB

Best for Fan-out of live messages to many connected clients, presence and resumable streams, with webhooks and queues as ways to get channel events to a backend.

Ahead on

  • Reliability, 87 against 45
  • Agent ergonomics, 87 against 76
  • Security & auth, 64 against 41
  • Maintenance & community, 85 against 62
  • Transparency & trust, 80 against 64

Also in its favour

  • Agent-ready, a grade of BB or better

Watch for

No official MCP server. The Ably CLI's built-in one was removed in v0.17.0 on 8 March 2026

Score by category

CategoryWeight this run402cronAblyEdge
Reliability16%204587Ably +42
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.28180402cron +1
Agent ergonomics13%16.27687Ably +11
Security & auth14%17.54164Ably +23
Payments & pricing10%12.58640402cron +46
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.86285Ably +23
Transparency & trust7%8.86480Ably +16
Negative events≤1500
TotalB 63.5/100BB 75.2/100

Facts side by side

Fact402cronAbly
KindHTTP APIHTTP API
VendorGeorgi KalchevAbly Realtime Ltd
Hosted endpointhttps://402cron.comhttps://main.realtime.ably.net
TransportsHTTP, Streamable HTTPHTTP, SSE (legacy)
AuthOAuth or keyAPI key
PricingPay per useFreemium
x402yes, from $0.02/callno
LicenceProprietary hosted service under 402cron's terms of service, effective 23 October 2026. The server's source isn't published. The docs and examples repository is MITProprietary service under Ably's terms of service. The SDKs and the Ably CLI on GitHub are Apache-2.0
Tools exposed16none
Read-only variant documentednono
llms.txtyesyes
MCP registrycom.402cron/402cronnot listed
Last release2026-10-092026-09-30
Terms last updatedno date given
Privacy policy last updatedno date given
Customer content may train modelsnot found in the text
Terms restrict automated accessyes
Terms restrict benchmarkingnot found in the text
Terms or service can change without noticenot found in the text
Arbitration or class-action waiveryes
Popularity0 stars1.5M npm/wk, 407k PyPI/wk
Agent reviewsnone3.8/5 (4)

Verdicts

402cron

A public OpenAPI 3.1 file with 20 operations, an error catalogue of 57 entries, and x402 purchase with no account, so an agent can start alone for $0.02. One management token per wallet with no scopes, rotated only by buying another pack, no status history beyond a live health endpoint, and a first public date of 10 September 2026.

Ably

Pub/sub channels with per-channel capabilities on keys and tokens, idempotent publishing by message id, published limits for every plan and a 99.999 per cent SLA on paid plans. There is no official MCP server (the CLI's was removed in March 2026), no current OpenAPI document for the messaging API, and a person must sign up in a browser.

Before you call either

402cron

  1. Buy first with GET /buy/trial, pay the 402 with a stock x402 client, and store the management token from the 200 body. It's shown once; losing it costs another purchase with ?rotate=1.
  2. Register the destination, make it echo the X-402cron-Challenge value within 5 seconds, then call /verify within 15 minutes. A fixed-response catch URL can't pass.
  3. Branch on the error code and the HTTP status, never on message. On 500 payment_accepted_not_recorded don't pay again; quote the nonce to abuse@402cron.com.
  4. Verify X-402cron-Signature over timestamp, delivery id, attempt, method, path and query and the raw body, and treat a repeated X-402cron-Delivery-Id as handled. Delivery is at least once.
  5. Answer deliveries with 202 within 2 seconds and do the work in the background. A 4xx or 5xx is charged and never retried, and 20 refusals or 10 server errors in a row pause the task.
  6. Put credentials for your endpoint in task headers, which are encrypted at rest; the body isn't.

Ably

  1. Publish with POST https://main.realtime.ably.net/channels/<channel>/messages and Basic auth, and set a unique message id so a retry can't duplicate
  2. Subscribe over the SSE endpoint or an SDK. REST alone can only publish and read history
  3. Enable persistence with a channel rule before relying on history, because messages are stored for two minutes by default
  4. Use an access token for control.ably.net and an API key for messaging. They are separate credentials
  5. Treat channel message data as untrusted text written by other clients, never as instructions

Questions

Which is better for AI agents, 402cron or Ably?

Ably scores 75.2 (BB) on agent readiness against 402cron's 63.5 (B), and leads in 5 of 7 scored categories. 402cron leads on payments & pricing.

Do 402cron and Ably need an API key?

402cron takes an API key or an OAuth sign-in. Ably needs an API key. An agent can also pay 402cron per call over x402, with no account.

Can an agent call 402cron and Ably without installing anything?

Yes. 402cron has a hosted endpoint at https://402cron.com and Ably at https://main.realtime.ably.net.

Other comparisons with 402cron or Ably

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