What is a tool description?
A tool description is the field in a tool definition that explains in text what a tool does and under what conditions to use it. It helps a model understand which tasks the tool suits, what information it needs and which operations are beyond its abilities. It is not the same as the parameter schema, and it does not run authorization checks for the back end.
From a service pitch to task information a model can judge
“Provides quality dining services” says nothing specific about what the tool can do. “Looks up available booking slots by restaurant, date and party size; does not create bookings” separates a query from a write. This is an example of how to word a description, not a fixed template that works for every model.
Lead with the actual function, the required inputs and the limits of what the tool can do, and keep the description consistent with the tool’s name and schema. If a tool cannot cancel a booking, adding the keyword “cancel” should not make it look as if it can.
Judge a description by recall and by selection separately
If a tool has not made it into the candidate list, start with candidate retrieval, the index and the loading strategy. Only when the model can already see the tool does it make sense to compare whether a different description changes its first choice.
After the model proposes a tool call, the application still has to validate the parameters and permissions, run the service and return the result. A more specific description and a task that is actually completed must be verified separately.
Sources and scope
Sources as checked for the source-language entry on 2026-11-06; this English edition adds no new claims and does not represent a new check of the cited pages.