> ## Documentation Index > Fetch the complete documentation index at: https://docs.superlog.sh/llms.txt > Use this file to discover all available pages before exploring further. # Create a synthetic check > Creates a check that requests a URL on a schedule and checks the response. After `failuresToAlert` failed runs in a row it posts to its Slack channel, and posts the recovery in the same thread. Defaults: GET, every 300 seconds, a 10 second timeout, 1 retry, alert after 1 failure, follow redirects, enabled. ## OpenAPI ````yaml /api-reference/openapi.json post /synthetic-checks openapi: 3.1.0 info: description: >- Manage a Superlog workspace's automations, runs, tag mode, model access, and secrets, read its telemetry, build dashboards and alerts over it, run synthetic checks, and export them to Terraform. Every request acts as the member who created the API key. title: Superlog management API version: 1.0.0 servers: - url: https://superlog.sh/api/v1 security: - bearerAuth: [] tags: - description: Connected integrations and the IDs automations and tag mode use. name: Integrations - description: The workspace and its members. name: Workspace - description: Keys that authenticate the management API and MCP server. name: API keys - description: Create and change automations. name: Automations - description: Start, follow, and cancel automation runs. name: Runs - description: What Superlog can use and change when someone mentions it in Slack. name: Tag mode - description: Model API keys, subscriptions, and available models. name: Models - description: Credentials agents can use without seeing them. name: Secrets - description: Read the workspace's logs, traces, and metrics. name: Telemetry - description: >- Exceptions in the workspace's telemetry, grouped into issues by fingerprint. name: Errors - description: Create and change dashboards over the workspace's telemetry. name: Dashboards - description: Threshold alerts on the workspace's telemetry that post to Slack. name: Alerts - description: HTTP checks that request a URL on a schedule and post failures to Slack. name: Synthetics - description: Configuration for the superloglabs/superlog Terraform provider. name: Terraform paths: /synthetic-checks: post: tags: - Synthetics summary: Create a synthetic check description: >- Creates a check that requests a URL on a schedule and checks the response. After `failuresToAlert` failed runs in a row it posts to its Slack channel, and posts the recovery in the same thread. Defaults: GET, every 300 seconds, a 10 second timeout, 1 retry, alert after 1 failure, follow redirects, enabled. operationId: create_synthetic_check requestBody: content: application/json: schema: type: object properties: assertions: maxItems: 20 type: array items: type: object properties: key: description: >- The header name for `header`, or the JSON path for `json_path`, such as `$.status`. type: string maxLength: 500 kind: type: string enum: - status_code - response_time - header - body - json_path - certificate_expiry description: >- What the assertion reads: the status code, response time in ms, a header, the body text, a JSON path, or days until the TLS certificate expires. op: type: string enum: - eq - neq - lt - gt - contains - not_contains - exists - not_exists description: >- `status_code` takes eq, neq, lt, gt; `response_time` lt; `header` eq, neq, contains, not_contains, exists, not_exists; `body` contains, not_contains; `json_path` all; `certificate_expiry` gt. severity: description: >- A failed `critical` assertion fails the run; a `degraded` one marks it degraded. Defaults to `critical`. type: string enum: - critical - degraded value: description: >- Compared with the response. A status code may be a class such as `2xx`. type: string maxLength: 1000 required: - kind - op description: >- Checks on the response. Without any, a run passes when the request completes. body: anyOf: - type: string maxLength: 65536 - type: 'null' description: The request body. Not for GET or HEAD. enabled: type: boolean description: A disabled check does not run. failuresToAlert: type: integer minimum: 1 maximum: 10 description: Failed runs in a row before the check posts to Slack. followRedirects: type: boolean headers: maxItems: 30 type: array items: type: object properties: name: type: string maxLength: 200 secret: description: >- Stores the value encrypted and never returns it. Defaults to false. type: boolean value: anyOf: - type: string maxLength: 8192 - type: 'null' description: >- The header value. For a secret header, null keeps the saved value while the URL keeps its host. MCP clients can only send null for a secret. required: - name - value description: Request headers. The list replaces the saved headers. intervalSeconds: type: integer description: >- How often the check runs: one of 60, 300, 900, 1800, 3600 seconds. method: type: string enum: - GET - HEAD - POST - PUT - PATCH - DELETE - OPTIONS name: type: string maxLength: 200 retries: type: integer minimum: 0 maximum: 2 description: Immediate retries before a run counts as failed. slack: anyOf: - type: object properties: channelId: type: string maxLength: 64 description: >- The Slack channel ID: the `channelId` of a channel alerts can post to. integrationAccountId: type: string format: uuid description: >- The ID of the Slack integration the channel belongs to. required: - channelId - integrationAccountId - type: 'null' description: >- Where failures and recoveries are posted. Without a channel the check only records its runs. timeoutMs: type: integer minimum: 1000 maximum: 30000 url: type: string maxLength: 2048 description: The full HTTP or HTTPS URL to request. required: - name - url required: true responses: '201': content: application/json: schema: type: object properties: check: type: object properties: assertions: type: array items: type: object properties: key: type: string kind: type: string enum: - status_code - response_time - header - body - json_path - certificate_expiry op: type: string enum: - eq - neq - lt - gt - contains - not_contains - exists - not_exists severity: type: string enum: - critical - degraded value: type: string required: - kind - op - severity - value additionalProperties: false body: anyOf: - type: string - type: 'null' createdAt: type: string enabled: type: boolean failuresToAlert: type: integer followRedirects: type: boolean headers: type: array items: type: object properties: name: type: string secret: type: boolean value: type: string required: - name - secret - value additionalProperties: false description: A secret header's value is always empty. id: type: string format: uuid description: Synthetic check ID. intervalSeconds: type: integer lastRunAt: anyOf: - type: string - type: 'null' lastStatus: anyOf: - type: string enum: - passed - degraded - failed - type: 'null' method: type: string enum: - GET - HEAD - POST - PUT - PATCH - DELETE - OPTIONS name: type: string retries: type: integer slack: anyOf: - type: object properties: channelId: type: string integrationAccountId: type: string required: - channelId - integrationAccountId additionalProperties: false - type: 'null' statusSince: anyOf: - type: string - type: 'null' description: When the check reached its last status. timeoutMs: type: integer updatedAt: type: string url: type: string webUrl: type: string format: uri description: The check in Superlog. required: - assertions - body - createdAt - enabled - failuresToAlert - followRedirects - headers - id - intervalSeconds - lastRunAt - lastStatus - method - name - retries - slack - statusSince - timeoutMs - updatedAt - url - webUrl additionalProperties: false required: - check additionalProperties: false description: Created '400': content: application/json: schema: $ref: '#/components/schemas/Error' description: The request is invalid. `issues` lists each invalid field. '401': content: application/json: schema: $ref: '#/components/schemas/Error' description: The API key is missing, revoked, or its creator left the workspace. '409': content: application/json: schema: $ref: '#/components/schemas/Error' description: >- The request conflicts with the current state, such as a name already in use. security: - bearerAuth: [] components: schemas: Error: type: object properties: code: description: A stable machine-readable error code, when there is one. type: string error: type: string description: What went wrong. issues: description: Validation problems, one per invalid field. type: array items: type: object properties: message: type: string path: type: array items: anyOf: - type: string - type: number required: - message - path additionalProperties: false required: - error additionalProperties: false securitySchemes: bearerAuth: description: A workspace API key, created in Superlog under Settings → API keys. scheme: bearer type: http ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.