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

Annotations already declare destructiveHint=false and non-idempotent, but the description adds a genuinely useful non-obvious trait: existing bookings in the block are not cancelled. It also warns that boundaries must be UTC, a real operational constraint.

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 tight sentences with no filler; the core action is stated first, followed by the non-cancellation caveat and the UTC requirement in priority order. Slightly dense but every sentence 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?

For a mutation tool with safety annotations and no output schema, the description covers the essentials: what it closes, that existing bookings survive, and the timezone contract. Nothing critical is missing, though a hint on what happens with overlapping blocks would round it out.

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%, so all five parameters are already documented, including the UTC example format. The description reinforces why UTC is required (schedule vs. respondent timezone drift) but adds no new syntax or constraints, so 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+resource — closing a time interval for bookings — and enumerates concrete cases (vacation, busy window, day off). It is clearly distinguishable from delete_booking_block and update_booking, though it does not name any sibling explicitly.

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?

Gives concrete use cases (vacation, busy window, day off), which implies when to reach for it, but offers no explicit when-not guidance or named alternatives (e.g., delete_booking_block to undo). Usage is implied rather than spelled out.

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