Errors

Every error returns a non-2xx status and the same JSON shape:

{
  "error": {
    "code": "unknown_keyboard",
    "message": "Unknown keyboard or size \"banana\". Use a size (100%, 98%, TKL, 75%, 65%, 60%) or one of these keyboards: …"
  }
}

Status	code	When
400	`missing_parameter`	A required query parameter is missing
400	`invalid_parameter`	A parameter is out of range or not one of the allowed values
400	`unknown_keyboard`	An item is neither a size nor a known keyboard
400	`unknown_size`	The `size` filter is not a known size
404	`unknown_size`, `unknown_keyboard`, `unknown_key`	The path names something that doesn't exist
404	`not_found`	No such endpoint
405	`method_not_allowed`	Only `GET`, `HEAD` and `OPTIONS` are supported

Messages are written for people and can change; match on code.