crontap-supabase-edge-function-cron

Schedule a Supabase Edge Function

Use Supabase pg_cron for SQL-only database maintenance. Use this pattern when the recurring unit is an HTTP Edge Function and an external scheduler is desired.

Prerequisites

Before using the required tools, check whether they are available. If any are missing, stop and offer the user exactly two choices:

1. Connect Crontap MCP at https://mcp.crontap.com/mcp. MCP access works on

every Crontap tier.

1. Configure $CRONTAP_CLIENT_ID and $CRONTAP_API_KEY for the raw API. Raw

API access requires Ultra.

Do not silently choose a path or continue until the user selects one.

• Deploy the function before creating its schedule.
• Make the function idempotent for one logical period.
• Protect it with a dedicated server-side cron secret.
• Never send a Supabase service-role key to Crontap.

Function security pattern

Read a dedicated header or bearer value and compare it with a server-only environment variable before doing work. If Supabase gateway JWT verification is disabled for the function, this application-layer check is mandatory.

Keep the function response bounded. For long work, durably enqueue the job and return success only after the queue accepts it.

Workflow

1. Deploy the Edge Function and configure its cron secret.
2. Call it manually from a controlled environment with and without the secret.
3. Confirm expected status codes and idempotency behavior.
4. Create the Crontap schedule with the deployed HTTPS URL.
5. Verify the resolved cadence and first retained run.

MCP example

{
  "tool": "create_schedule",
  "arguments": {
    "url": "https://project-ref.supabase.co/functions/v1/nightly-cleanup",
    "text": "every day at 02:00",
    "timezone": "UTC",
    "method": "POST",
    "headers": {
      "Authorization": "Bearer <cron-secret-from-secure-store>",
      "Content-Type": "application/json"
    },
    "body": {
      "source": "crontap"
    },
    "label": "Supabase nightly cleanup"
  }
}

Use the real project reference from the Supabase project URL. Do not place a secret in the function URL or JSON body.

REST fallback

REST requires Ultra API access:

curl --fail-with-body https://api.crontap.com/v1/schedule \
  -X POST \
  -H "ClientId: $CRONTAP_CLIENT_ID" \
  -H "ApiKey: $CRONTAP_API_KEY" \
  -H "Content-Type: application/json" \
  --data '{
    "url": "https://project-ref.supabase.co/functions/v1/nightly-cleanup",
    "interval": "0 2 * * *",
    "timezone": "UTC",
    "verb": "POST",
    "headers": {
      "Authorization": "Bearer <cron-secret-from-secure-store>",
      "Content-Type": "application/json"
    },
    "data": {"source": "crontap"},
    "label": "Supabase nightly cleanup"
  }'

Prefer MCP when available.

Verification

• A request without the cron secret returns 401 before side effects.
• A request with the secret returns the intended success status.
• Two requests for the same logical period create one durable side effect.
• The Crontap history outcome matches Supabase function logs at the same time.

Safety and plan limits

• Do not use SUPABASE_SERVICE_ROLE_KEY as the scheduler credential.
• Scope the function to the narrow recurring operation.
• If the Supabase project can pause, remember that an external clock exposes

the failure but cannot make an unavailable project execute.

• If Crontap rejects the cadence or capacity, present the returned four-option

ladder and smallest viable option.

Troubleshooting

• Supabase 401 means gateway or function authorization rejected the request.
• Supabase 404 usually means the project reference, function slug, or deploy

environment is wrong.

• A 2xx with missing work requires application logs and an idempotency-record

check.

• Timeouts are better fixed with durable queueing than aggressive retries.

References

• Crontap Agent Skills catalogue
• Supabase cron jobs
• Supabase Edge Function cron jobs
• Cron troubleshooting
• Live REST API reference