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

With no annotations the description carries the full burden, and it discloses meaningful behavior: confirm-gating (preview vs execute), the downstream coupling to booking slot generation, and the existence of two input forms. It omits mutation semantics such as whether an update replaces or merges existing availability, and any permission/authorization requirements.

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 core action, then the effect, then the syntax guidance and example. Dense and largely waste-free, though the parenthetical '(confirm-gated)' slightly duplicates the schema's own confirm parameter description.

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?

For a 7-param mutation tool with no annotations and no output schema, the description covers the core action, effect, and primary parameter but leaves required-parameter formats and update semantics (replace vs merge, effect on existing bookings) unaddressed.

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 only 14%, so the description must compensate, and it does so well for the hardest param (timeRanges, with a concrete example and the 'slots are only offered inside them' rule) plus the legacy checkIn/checkOut pair. However, the required params preferredTime, daysAvailable, and timezone get no explanation in either place, leaving a real 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 ('Update when the coach is bookable for sessions') and clarifies the scope by naming the downstream feature it drives (trainerAvailableHourSlotsNext7Days / session booking). An agent can tell exactly what the tool mutates 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?

Explicitly flags the confirm-gate behavior and gives form-selection guidance: use timeRanges for split hours, and 'checkIn/checkOut is the older single-window form,' implying the preferred alternative. It does not name when-not-to-use this tool, so it stops short of full routing guidance.

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