---
title: "Create monitor"
method: POST
path: "/monitors"
tags: ["Monitors"]
---

# Create monitor

`POST /monitors`

Creates an instant monitor. Monitors are unlimited. Active monitors check every 1 second and cost 21 credits per hour. Events and webhook deliveries are included. Creation requires available credits for the first hourly charge and username lookup.

## Request body

- object
  - `username` string, required — X username (without @)
  - `eventTypes` EventType[], required — Array of event types to subscribe to.

## Response `201`

Monitor created

- object
  - `id` string, required
  - `username` string, required
  - `xUserId` string, required
  - `eventTypes` EventType[], required — Array of event types to subscribe to.
  - `isActive` boolean, required
  - `createdAt` string, date-time, required
  - `nextBillingAt` string, date-time, required — Next hourly credit charge time. New active monitors are due immediately.

## Other responses

- `400` — Invalid input
- `401` — Unauthenticated
- `402` — Payment required. Fixed-price direct MPP requests return a Machine Payments Protocol problem document and a WWW-Authenticate challenge. Authenticated X data requests return balances and explicit Stripe checkout-creation actions. Guest paid-read keys receive only the accountless guest top-up action. Direct MPP challenges also advertise the Stripe wallet action. Other authenticated endpoints return a legacy error shape. A failed request never creates checkout. Create checkout only after the user confirms a payment option.
- `404` — X user not found
- `409` — Monitor already exists
- `429` — Xquik tier rate limit exceeded. The response includes a `Retry-After` header with the number of seconds to wait before retrying.

## Changes

- **2026-07-22** `37e31f0b5439` — 1 breaking, 384 warning
  - added `#/components/schemas/XWritePaymentRequired` to the response body `oneOf` list for the response status `402` (media type: application/json)
  - added the new `body_too_large` enum value to the `allOf[#/components/schemas/Error]/error/oneOf[subschema #1: LegacyErrorCode]/` response property for the response status `429`
  - added the new `body_too_large` enum value to the `allOf[#/components/schemas/Error]/error/oneOf[subschema #2: StructuredError]/code` response property for the response status `429`
  - added the new `body_too_large` enum value to the `error/oneOf[subschema #1: LegacyErrorCode]/` response property for the response status `400`
  - …381 more
  - …this revision’s changelog is incomplete
- **2026-07-13** `83005363f122` — 11 breaking, 17 warning, 123 info
  - added `#/components/schemas/AuthenticatedPaymentRequired, #/components/schemas/GuestPaymentRequired, subschema #3` to the response body `oneOf` list for the response status `402`
  - the response's body type changed from `object` to no type for status `402`
  - added `subschema #1: LegacyErrorCode, subschema #2: StructuredError` to the `error` response property `oneOf` list for the response status `400`
  - added `subschema #1: LegacyErrorCode, subschema #2: StructuredError` to the `error` response property `oneOf` list for the response status `401`
  - …147 more
- …earlier changes not shown

[Full history](https://skmtc.dev/xquik-dev/apis/xquik-api/changes/monitors/post.md)

---

[API](https://skmtc.dev/xquik-dev/apis/xquik-api.md) · [All operations](https://skmtc.dev/xquik-dev/apis/xquik-api/llms.txt) · [OpenAPI document](https://skmtc-service-production.skmtc.workers.dev/v1/apis/xquik-dev/xquik-api/revisions/37e31f0b5439/schema)