Documentation Index
Fetch the complete documentation index at: /llms.txt
Use this file to discover all available pages before exploring further.
The error envelope shape and what each error code means
{
"success": false,
"error": {
"code": "validation_error",
"message": "Some fields need attention.",
"fields": {
"qty": "must be greater than 0"
}
}
}
fields is only present when code is validation_error, it’s a map of field name to a plain-English problem description.
| Code | What it means |
|---|---|
invalid_request | The request itself is malformed, bad JSON, missing required structure. |
unauthorized | Your API key is missing, malformed, unknown, revoked, or expired. See Authentication, all of these return the same generic message on purpose. |
not_found | The resource doesn’t exist, or belongs to a different organization than your key’s (from your key’s perspective, those look identical). |
validation_error | One or more fields failed validation. Check the fields object for specifics. |
conflict | Something you’re creating collides with something that already exists, for example, reusing an invoice no that’s already in use in your organization. |
rate_limited | You’ve hit the per-resource rate limit. See Rate Limits. |
method_not_allowed | You used an HTTP method the endpoint doesn’t support. |
server_error | Something went wrong on Billbooks’ side. If this persists, get in touch. |
not_found covers both “doesn’t exist” and “belongs to someone else,” you can’t use it to probe whether a given ID exists in another organization, both cases look the same from the outside.