In FastBound API methods, you will often see fields named externalId or with externalId in their name.
In FastBound, an External Identifier provides integrated applications with a place to store identifiers from their applications on acquisitions, contacts, dispositions, and items in FastBound.
External Identifiers are optional, but if provided, each External Identifier must be unique, per FastBound account, and object type. In other words, each acquisition, contact, disposition, and item must have a unique External Identifier.
If an External Identifier has already been used in a given FastBound account, FastBound will reject the request with an error message similar to the following:
External ID {externalId} is already used on an {object type}.
