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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), and the description adds genuinely new behavior: the three causes of an empty list (closed, full, minimum notice), the required scope (appointments:read, any member), and the constraint that returned startTime values must be passed unchanged. That is substantial context beyond structured fields.

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?

A single dense paragraph front-loaded with the purpose and the call-order obligation, then the date semantics, return shape, empty-list meaning, and auth scope. Every sentence carries information an agent needs; nothing is redundant.

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?

There is no output schema, and the description compensates by describing the return shape ([{ startTime, endTime, displayTime }]) with formats and an example, plus the empty-list case. For a 3-required-param read tool, nothing needed to call it correctly is missing.

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 description coverage is 100% and already documents that date is YYYY-MM-DD in the location's timezone and where locationId/appointmentTypeId come from. The description restates the timezone point for date but adds no format or constraint detail the schema lacks, so the baseline 3 is appropriate.

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 with scope: "List the start times a carrier can book for one appointment type on one day." An agent can immediately distinguish this availability-query tool from siblings like create_appointment or list_appointments without opening any 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?

Explicitly says when to call it ("before create_appointment or reschedule_appointment: only these times are accepted") and routes the agent elsewhere for a related question ("get_location_setup explains why" an empty list occurs). Both the precondition and the fallback are stated, not implied.

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