Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With readOnlyHint/idempotentHint already declaring the safe-read profile, the description adds real behavioral context: results are restricted to the appointment's own service and provider, and the range is bounded by date_from/date_to. It omits pagination/result-size behavior, but the output schema covers return shape.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Two tight sentences, front-loaded with the action and scope, followed by the one piece of provenance an agent needs. No filler or restated schema text.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a read-only lookup with an output schema, the description supplies the essential scoping rule, the date-range bound, and the source of appointment_ref; return values need not be explained. Only action_id is left implicit, a minor omission.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 50%: date_from/date_to are already documented in the schema, and the description only re-frames them as a range. It does add provenance for appointment_ref, but the required action_id parameter remains unexplained in both schema and description, which is a meaningful gap.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

Specific verb (List) plus precise resource (open times an appointment can move to), with the scoping rule 'for its own service and provider' that separates it from generic slot-listing siblings like list_xona_booking_slots. An agent can tell what it returns without opening the schema.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives clear context for use (finding reschedule options for an existing appointment) and even states where appointment_ref comes from (list_xona_appointments). It does not, however, name a contrasting sibling such as list_xona_booking_slots for brand-new bookings, nor state prerequisites about appointment status.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.