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

Annotations already mark the tool read-only and non-destructive, and the description adds genuinely useful behavioral detail: the two response modes, the 90-day horizon, the offeredDurations on each slot, and the subtle 'null means offered but not bookable through the API' rule. Nothing contradicts the annotations.

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?

Three dense, front-loaded sentences with no filler: the core operation comes first, the mode selection follows, and the output/booking nuance closes. Every clause earns its place.

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?

Despite having no output schema, the description specifies the two response shapes, the durationId linkage, and the non-bookable null case, so an agent has enough to call the tool and interpret results. It is complete for a moderately complex two-mode lookup tool.

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?

With 0% schema description coverage, the description carries the full parameter burden and does so well: it explains the captainSlug/boatId mutual exclusivity, the date format, and the role of durationHours in selecting the slot mode. It adds meaning the bare schema lacks.

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?

The description opens with a specific verb and resource: 'Check a captain's or boat's availability.' It then clarifies the two distinct query modes, which separates it from sibling detail tools like get_captain/get_boat and from downstream booking tools like create_booking.

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?

'Provide exactly one of captainSlug or boatId' is an explicit parameter exclusion, and the description gives precise conditional instructions: omit date for a 90-day date list, provide both date and durationHours for slots. It also routes the resulting durationId to get_quote, create_booking, or create_boat_rental, explaining the downstream context.

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