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Your application talks to Output through a REST API. When you deploy Output, the API server exposes HTTP endpoints for running workflows, checking their status, and retrieving results. Your backend sends a request, Output orchestrates the workflow, and you get structured results back. During development, the API server starts automatically on port 3001 when you run output dev.

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Two Ways to Run Workflows

Choose based on how long your workflow takes and how your application handles responses.

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Run and Wait (Synchronous)

POST /workflow/run blocks until the workflow completes and returns the result in the response body. Use this when workflows complete quickly (seconds) and your client can wait. 
curl -X POST http://localhost:3001/workflow/run \
  -H "Content-Type: application/json" \
  -d '{"workflowName": "summarize_url", "input": {"url": "https://example.com/article"}}'

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Start and Poll (Asynchronous)

POST /workflow/start returns the workflow ID immediately. Poll for status and retrieve the result when ready. Use this for longer workflows — minutes or more — where blocking a request isn’t practical. 
# Start the workflow
curl -X POST http://localhost:3001/workflow/start \
  -H "Content-Type: application/json" \
  -d '{"workflowName": "company_research", "input": {"domain": "example.com"}}'

# Check status
curl http://localhost:3001/workflow/<workflow-id>/status

# Get result when completed
curl http://localhost:3001/workflow/<workflow-id>/result

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Interacting with Running Workflows

Output supports sending data to running workflows and reading their state via signals, queries, and updates. The workflow must define handlers for these — see External Integration for how to set them up.
MethodWhat it doesUse case
Signal POST /workflow/:id/signal/:namePush data into a workflowHuman approval, external events
Query POST /workflow/:id/query/:nameRead workflow state without changing itProgress checks, status dashboards
Update POST /workflow/:id/update/:nameChange state and get confirmationConfiguration changes, priority updates

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Stopping Workflows

  • PATCH /workflow/:id/stop — Graceful stop. Allows cleanup handlers to run.
  • POST /workflow/:id/terminate — Force terminate. Immediate, no cleanup.

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Workflow Discovery

GET /workflow/catalog returns all available workflows with their input and output schemas. Use this to build dynamic UIs or validate inputs before submitting.

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Debugging

GET /workflow/:id/trace-log returns the full execution trace for a completed workflow. See Tracing for the trace format.
For remote traces, the API server needs AWS credentials (OUTPUT_AWS_ACCESS_KEY_ID, OUTPUT_AWS_SECRET_ACCESS_KEY, OUTPUT_AWS_REGION).

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What’s Next

Configuration

Base URL, ports, and environment variables for the API server.

Authentication

How auth works in development vs production.

Error Responses

Error codes, response format, and how to handle failures.