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

Annotations only carry the generic hint set, so the description carries real weight and delivers: the one-upcoming-free-call-per-person refusal condition, that the refusal names the existing booking, that nothing is charged, and that the invite originates from cal.com. It even explains the returned booking's label and join link and how to move or cancel it.

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 constraint, and every sentence carries operational information. It is dense and repeats 'free 30-minute intro call with Ben' several times, which costs a point on tightness but not on clarity.

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?

With no output schema, the description compensates by describing the resulting booking object (own label and join link) and the tools that operate on it. Combined with the eligibility rules and refusal behavior, 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 baseline is 3; the description goes beyond it by constraining 'start' to be passed exactly as my_bookings lists it and to be named by its label rather than a computed weekday. Topic and timeZone semantics are left entirely to 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 ('Book the signed-in person a free 30-minute intro call with Ben') and implicitly separates itself from the sibling book_hour_with_ben by naming the 30-minute intro call. An agent can tell exactly what this does 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?

Explicit when-to-offer (Forge Pass / working with Ben one-to-one, incl. Captain on Deck), explicit when-not (never for Pirate Pass or event tickets), and explicit routing ('Book it here: do not send the person to a booking page unless this refuses or fails'). It also names the follow-up alternatives move_booking and cancel_booking.

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