Agent File is intended to support "one thread" agents, ie agents that have an indefinite conversation/event history, even if the underlying in-context message history is limited. That's why there's a distinction between just "messages" and "in-context messages" (a subset of messages).
If you're interested in the full schema you can look at the Pydantic models here: https://github.com/letta-ai/letta/blob/main/letta/serialize_...
Agent File is intended to support "one thread" agents, ie agents that have an indefinite conversation/event history, even if the underlying in-context message history is limited. That's why there's a distinction between just "messages" and "in-context messages" (a subset of messages).