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

Goes well beyond the annotations: no charge, the diamond is retained for an hour, the intro call stays free, the calendar invite is re-sent, and the response carries the new label. It also enumerates the exact refusal reasons, which nothing in the structured fields conveys. Annotations (non-read-only, non-destructive, non-idempotent, closed-world) are consistent and supplemented rather than repeated.

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?

Front-loaded with the action and scope, and every sentence carries information (sources, charge behavior, refusal cases). It is a single dense paragraph with stacked parentheticals, so it is readable but heavier than it needs to be.

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?

No output schema exists, yet the description states what the answer contains (the booking with its new label) and what failure looks like (a refusal with a reason). Combined with prerequisites, charging behavior, and per-kind start sources, an agent has everything needed to call this correctly.

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 100%, so the baseline is 3, but the description adds real operational meaning: 'start' must be copied exactly as listed and named by its label rather than a weekday the agent computes, which guards against a common failure mode. It is silent on the timeZone parameter, which is covered only by the schema.

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 ('Move one of the signed-in person's own upcoming bookings') and immediately narrows scope to exactly two bookable kinds (the free intro call, an hour with Ben). It is clearly distinguishable from book_hour_with_ben, book_intro_call, and cancel_booking 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 routes the agent to my_bookings and the canMove flag for eligible bookings, then tells it where each kind's target start must come from (openHours vs introCall.moveTimes). It also lists the refusal conditions (not theirs, cancelled, begun, awaiting calendar, time not open), which is effectively a when-not-to-expect-success guide.

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