> ## Documentation Index
> Fetch the complete documentation index at: https://docs.doola.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Errors

> JSON-RPC errors, auth challenges, tool-level failures, and how to recover.

## Transport errors

Returned as JSON-RPC errors on the HTTP response:

| Code     | HTTP | Meaning                                                                                           |
| -------- | ---- | ------------------------------------------------------------------------------------------------- |
| `-32600` | 400  | Missing `Mcp-Session-Id` header on a non-`initialize` request. Echo the header from `initialize`. |
| `-32603` | 500  | Internal error. The body's `error.message` includes the underlying cause.                         |

## Auth challenges

A `401 Unauthorized` (with a `WWW-Authenticate` challenge) is returned when the bearer token is missing, malformed, or inactive. Re-authenticate via the [OAuth flow](/mcp/authentication).

## Tool-level failures

Validation rejections, missing state, precondition gates, and backend errors are **not** JSON-RPC errors. Per the MCP spec they surface inside the successful response's `result.content`. Inspect `result.isError` and the embedded `error` / `code` / `message`.

For `advance_company_onboarding`, error responses carry the same steering fields as success — follow `nextAction` and `nextActionInput` rather than retrying the same call:

| `code`                   | Meaning                                                                                                      |
| ------------------------ | ------------------------------------------------------------------------------------------------------------ |
| `INVALID_INPUT`          | Missing or malformed `action` / `params`.                                                                    |
| `UNKNOWN_ACTION`         | The `action` isn't one of the supported values.                                                              |
| `PRECONDITIONS_NOT_MET`  | Earlier steps are incomplete. `missing` lists them in flow order; `nextActionInput` is the step to do first. |
| `READINESS_CHECK_FAILED` | A transient backend issue while verifying state. Retry in \~10 seconds.                                      |
| `FILING_FAILED`          | The submission couldn't be filed. The `message` explains what to retry.                                      |

## "No active session"

The most common runtime failure is a missing or expired identity — typically an expired token. Recover by **re-authenticating** (the bearer is the source of identity), then call `get_company_onboarding_status` to confirm where to resume. Don't redo steps the customer already completed.