> ## Documentation Index > Fetch the complete documentation index at: https://docs.duraton.ai/llms.txt > Use this file to discover all available pages before exploring further. # Errors > Work out what went wrong and what to do about it: the error body, the status codes the API returns, and how to handle each in the SDK and over MCP. Every failed request returns a JSON body with an `error` field and an HTTP status code: ```json theme={null} { "error": "run already in a terminal state" } ``` The status code tells you the class of failure; the `error` string is a short, human-readable reason. ## Success codes ```sh theme={null} curl -sS -o /dev/null -w "%{http_code}\n" -X POST "$DURATON_URL/events" \ -H "Authorization: Bearer $DURATON_API_KEY" \ -d '{"name":"ticket.created","app":"support-app","data":{"ticketId":"T-421"}}' # 202 ``` | Status | Returned by | | ---------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | `200 OK` | Every read, the control writes (`cancel`, `pause`, `resume`, `replay`, `retry-from-step`, `bulk-replay`), an approval decision, a `PATCH` on a webhook endpoint/source, and `POST /webhook-source-deliveries/{id}/replay` (returns the replay outcome). | | `201 Created` | `POST /webhook-endpoints`, `POST /webhook-sources`. | | `202 Accepted` | `POST /events` and `POST /webhooks/{token}` - the event is recorded; the runs it starts are asynchronous. | | `204 No Content` | `DELETE /webhook-endpoints/{id}`, `DELETE /webhook-sources/{id}`, `POST /webhook-deliveries/{id}/redeliver`. | ## Status codes | Status | Meaning | | --------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | `400 Bad Request` | The request body is malformed, or a field is invalid - an event names a workflow that isn't registered, an event carries an [unsupported character](/reference/api/events#unsupported-characters), an approval decision isn't `approved`/`denied`, or a `GET /webhook-source-deliveries?status=` value is outside the [accepted set](/reference/api/webhooks#the-inbound-delivery-log). | | `401 Unauthorized` | The API key is missing or unknown. | | `403 Forbidden` | A read-only (public) key attempted a write, or the project is suspended after its workspace reached the plan limit. | | `404 Not Found` | The addressed resource - run, step, event, approval, or webhook source/endpoint/delivery - does not exist. | | `409 Conflict` | The request conflicts with current state (see below). | | `501 Not Implemented` | The requested capability isn't configured for this project (for example, failure explanations when no model is wired up). | | `502 Bad Gateway` | The status reserved for a runner-not-registered condition. Note that triggering a run against an app with no live [runner](/core/runners) does **not** return this: `POST /events` is still accepted (`202`) and the run [parks and retries](/core/runners#when-no-runner-is-registered), failing terminally only after the bounded no-runner wait elapses. | | `500 Internal Server Error` | An unexpected fault. The body is a generic `{ "error": "internal error" }`; the detail is logged server-side and never returned. | ## Conflicts (409) A `409` means the resource is in a state that doesn't allow the operation. The common cases: | `error` | Cause | | ----------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------ | | `run already in a terminal state` | Pausing, resuming, or cancelling a run that already succeeded, failed, or was cancelled. | | `run is not in a terminal state` | Replaying a run that hasn't finished. | | `run is not paused` | Resuming a run that isn't paused. | | `run is not awaiting a decision` | Deciding an approval on a run that isn't waiting for one. | | `approval is not open` | Approving or denying an approval that was already decided. | | `step attempt already recorded` | A duplicate step result (a runner retried after Duraton already recorded the step). | | `webhook token already in use` | Creating an inbound source whose issued receive URL token collides (rare - the token is random). | | `webhook source name already in use` / `webhook endpoint name already in use` | A source/endpoint name isn't unique in the project. | | `webhook endpoint url already subscribed` | The outbound URL is already registered in the project. | | `webhook delivery is in flight` | Redelivering a webhook whose current attempt hasn't settled. | Conflicts are safe to surface to the caller and, where they reflect a race (a duplicate step, an in-flight delivery), safe to ignore. ## Handling errors Check the status code and read the `error` field: ```sh theme={null} curl -sS -o /tmp/body -w "%{http_code}" \ -X POST "$DURATON_URL/runs/$RUN_ID/resume" \ -H "Authorization: Bearer $DURATON_API_KEY" # 409 cat /tmp/body # { "error": "run is not paused" } ``` The client throws `DuratonApiError`, which carries the `status` and raw `body` and has helpers for the common classes: ```ts theme={null} import { createClient, DuratonApiError } from "@duraton/sdk/client"; const duraton = createClient({ url: process.env.DURATON_URL!, apiKey: process.env.DURATON_API_KEY!, }); try { await duraton.runs.resume(runId); } catch (err) { if (err instanceof DuratonApiError) { if (err.isConflict()) { // 409: the run wasn't paused - already resumed or finished } else if (err.isNotFound()) { // 404 } else { console.error(err.status, err.body); } // also: err.isBadRequest(), err.isUnauthorized(), err.isForbidden() } } ``` When a tool call fails, the [MCP server](/integrations/mcp-server) returns the same reason as the tool result's error - for example, calling `resume_run` on a run that isn't paused returns `run is not paused`. Unexpected server faults are masked to `internal error`, exactly as over REST, and a write tool called with a read-only key returns `this tool requires a full-access (secret) API key`.