## Quick checklist

1. Call [`/connectToServer`](/api-reference/connectToServer) and save the `userToken`.
2. *(optional)* Load environment data — [`/loadFuel`](/api-reference/loadFuel), [`/loadAspect`](/api-reference/loadAspect), [`/loadSlope`](/api-reference/loadSlope), [`/loadWindFlow`](/api-reference/loadWindFlow).
3. Configure the simulation — `setCellResolution`, `setWindCondition`, `setPointIgnition`, `setMultiParameters`, etc.
4. Run [`/runSimulation`](/api-reference/runSimulation) (single interval) or step with [`/continueSimulation`](/api-reference/continueSimulation) (repeated intervals).
5. Query results only after the simulation has run (some endpoints return **500** before that).

## Reading responses

Each [API reference](/api-reference) endpoint lists **Responses** tabs (200, 400, 500).

| Status | Typical meaning |
|--------|-----------------|
| **200** | Success — plain text or JSON depending on endpoint |
| **400** | Bad request — often empty body; invalid types or empty file upload |
| **500** | Spring Boot error JSON — missing or invalid `userToken`, missing params, or wrong call order (not HTTP 401) |
  Missing or invalid `userToken` returns **500** with `{"error":"Internal Server Error",...}`, not 401. The server cannot locate a simulation instance for an unrecognized token.

## Common pitfalls

- **`getCellState`**, **`getPerimeterCells`**, **`computeBurnedArea`** — may return **500** before `runSimulation` or `continueSimulation` has been called.
- **`runSimulation` / `continueSimulation`** — the `time` parameter must be greater than 0. An empty array response means the computed fire perimeter is empty, which usually indicates a backend error or a misconfigured API call.
- **`continueSimulation`** — does not require `runSimulation` to be called first; use it on its own to run in steps.
- **Load endpoints** — require a non-empty `text/plain` body and `fileName` header. `loadFuel`, `loadSlope`, and `loadAspect` also update `cellResolution` from the file's `cellsize` field. [`loadWindFlow`](/api-reference/loadWindFlow) uses the SIMS `ncols` / `nrows` file format.
- **`setDynamicIgnition`** — passing an invalid `mode` value returns **400**.