Lead fields represent the near-complete schema for a lead in the context of the company of the authorized user. Each company can have a different schema for their leads, with various custom fields. In the context of using lead fields as a schema for defining the data fields of a lead, it must be kept in mind that some types of custom fields can have additional data fields which are not separate lead fields per se. Such is the case with monetary, daterange and timerange fields – each of these fields will have one additional data field in addition to the one presented in the context of lead fields. For example, if there is a monetary field with the key ffk9s9 stored on the account, ffk9s9 would hold the numeric value of the field, and ffk9s9_currency would hold the ISO currency code that goes along with the numeric value. To find out which data fields are available, fetch one lead and list its keys.