# SchedStack: durable scheduled HTTP delivery

> A destination plus a time, delivered and retried until it lands, never silently lost. Durable scheduling for the agentic era.

SchedStack is durable scheduled HTTP delivery. You hand it a destination and a time (one-shot or recurring), over a REST API or an MCP server, and it delivers, retries until it lands, and never silently loses an accepted delivery. It is agent-native, DST-correct on recurrence, and publishes a 100–300 ms p99 dispatch-initiation SLO.

## Create a schedule

```bash
curl https://api.schedstack.com/v1/schedules \
  -H "Authorization: Bearer sk_live_..." \
  -H "Content-Type: application/json" \
  -d '{"endpoint":"https://api.acme.com/hooks/billing","delay":"24h"}'
```

## Why SchedStack

- **Schedule in plain language.** A first-class MCP server lets agents schedule the future as "in 2h", ISO, or cron, with a next-fire preview before anything commits.
- **Never silently lost.** At-least-once made safe with signatures and idempotency. Failures land in dead-letter, replayable on demand. Nothing dropped on the floor.
- **DST-correct recurrence.** Spring-forward and fall-back handled correctly. "9am local" stays 9am across the change, with no double-fires and no skips.
- **Published accuracy SLO.** A stated 100–300 ms p99 dispatch-initiation SLO. We publish the number instead of hand-waving about reliability.
- **Test and live modes.** Isolated test and live modes from day one, Stripe-style. Build and verify against test data without ever touching production.
- **Failure-path pricing.** Retries do not multiply your bill. You are not punished for the failures SchedStack exists to handle.

## How it compares

| Capability | SchedStack | QStash | Posthook | Inngest | Cron |
| --- | --- | --- | --- | --- | --- |
| Scheduled HTTP delivery | Core | Yes | Core | Via steps | Manual |
| No SDK required (just HTTP) | Yes | Yes | Yes | SDK | n/a |
| Agent-native MCP server | Yes | No | No | No | No |
| DST-correct recurrence | Yes | Limited | Yes | Limited | No |
| Published accuracy SLO | Yes | No | No | No | No |
| Dead-letter + replay | Yes | Yes | Yes | Yes | No |

## FAQ

### How can an AI agent schedule a task to run later?

An agent cannot hold a timer inside a single model call, so it needs an external service that owns the clock. SchedStack exposes an MCP server: your agent calls create_schedule with a destination and a time, and SchedStack calls your endpoint back at the right moment, retried until it lands.

### What is SchedStack?

SchedStack is durable scheduled HTTP delivery. You hand it a destination and a time, one-shot or recurring, and it delivers, retries until it lands, and never silently loses an accepted delivery.

### How is it different from QStash or a cron job service?

Cron dies with the host and keeps no record. QStash is a messaging platform where scheduling is one feature. SchedStack is built around scheduling: DST-correct recurrence, a published accuracy SLO, and a first-class MCP server.

### Can I try it without touching production?

Yes. SchedStack has isolated test and live modes from day one. Build and verify in test mode, then flip to live. Test data never mixes with production.

### What does "never silently lost" mean?

Once SchedStack accepts a schedule, it owns delivery end to end: it retries with backoff until your endpoint confirms, and on exhaustion the delivery lands in a dead-letter queue you can inspect and replay. It is never dropped without a trace.

### How do I verify a delivery really came from SchedStack?

Every outbound request is signed. Verify the Sched-Signature header (HMAC-SHA256 over timestamp, delivery id, attempt, method, path, and body) and dedupe on the Idempotency-Key. Receiver code samples are in the docs.

### What is the accuracy SLO?

SchedStack publishes a 100–300 ms p99 dispatch-initiation SLO: the time from a schedule becoming due to dispatch beginning.

### Does it handle time zones and DST?

Yes. Recurring schedules are DST-correct: "9am local" stays 9am across spring-forward and fall-back, with no double-fires or skips.

## Links

- Docs: https://schedstack.com/docs/
- API reference: https://schedstack.com/docs/api/
- llms.txt: https://schedstack.com/llms.txt