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

Annotations already declare read-only, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds real behavioral detail beyond that: how results are ranked (closest ten to preferred_time, else balanced spread, plus earliest open time) and that an empty result carries a reason.

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 sentences, front-loaded with what the tool returns and immediately followed by the range constraint and the handoff token (slot_fingerprint). Dense but every clause carries information; no filler.

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?

An output schema exists, so return values need not be explained, yet the description usefully signals ranking behavior and the empty-case reason. Combined with annotation coverage of the safety profile, an agent has enough to call this correctly; the only gap is guidance on choosing it over the public slot listing.

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 67%, so the schema already documents date_to, date_from, doctor_id and preferred_time in detail. The description reinforces the date semantics ('inclusive, at most 8 weeks out') but says nothing about practice_slug, service_id or doctor_id, so it only partially compensates for the coverage 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?

States a specific verb and resource ('List open times at a connected practice for one service') with an explicit date-range scope, which separates it from the service-listing and public-slot siblings. It stops short of naming an alternative tool the way a 5 would.

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?

It gives boundary conditions (inclusive range, at most 8 weeks out, at most 56 days) and forward-routes to hold_xona_booking_slot, so usage is implied and partially guided. There is no explicit 'use this instead of list_public_booking_slots when...' statement, leaving the connected-vs-public choice to inference.

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