# Identifiers

**Identifiers** are OddsFinder typed identifiers: a kind prefix, an underscore and a decimal sequence number (`fx_1839204`, `tm_3041`, `dec_12`). The prefix is part of the identity, so each parameter states the kind it expects. An identifier whose prefix does not match the parameter's kind, or whose body is not a plain decimal number (a bare UUID, leading zeros, letters), is a `400 invalid-request` naming the parameter; a well-formed identifier that does not exist is a `404 not-found`. When two records turn out to be the same entity they are merged and one identifier is retired; a retired identifier keeps resolving, and the response carries a `resolution` object naming the requested and the canonical identifier.