Invalid amount

What it means

An amount field was not a decimal string.

Example detail messages returned with this error:

• amount_eur must be a decimal string such as “12.50”; omit it to refund the remainder.

What to do

Send the amount as a string in major units, with a decimal point: "12.50", not 12.5 and not 1250. A string is required because binary floating point cannot represent most decimal amounts exactly, and a rounding error in a money field is a real discrepancy rather than a display artefact.

To refund everything still outstanding, omit the field entirely rather than computing the remainder yourself — the server knows what has already been refunded.

Response shape

All fremforge API errors are RFC 9457 problem+json:

{
  "type": "https://docs.frem.sh/reference/api/errors/invalid-amount",
  "title": "Bad Request",
  "status": 400,
  "detail": "..."
}

Branch on type, not on title or detail - those are human-readable and may be reworded.