The metadata parameter in the Conversation API allows you to pass information on messages, conversations, and contacts. Metadata can be compared to a tag in that it provides information on the message or contact but is not a part of the message itself.
The metadata field is a string up to 1024 long.
A few ways other users have used the metadata fields:
Distinguish messaging campaigns from one another using a code
Assign various codes to departments to know who sent the message
Distinguish one messaging author from another
Additional validation security
Specify an objective of the message sent
Name groups of contacts
More specific regional information on a group of contacts.
Retrieving self-appointed metadata can become a powerful tool when reviewing analytics.