Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given the tool's simplicity (no output schema, all parameters optional, no nested objects), the description provides a complete enough picture: it specifies the time window (7-day), the content (LLM spend digest), and the breakdown dimensions. It does not detail the exact response format, but for this straightforward read tool, the description is sufficient.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.