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

Annotations already declare destructiveHint=true, openWorldHint=true, idempotentHint=false. The description adds the behavioral consequence (clients cannot book the slot) but does not explain conflict handling, whether an existing appointment in that window is affected, permissions needed, or how to undo the block – gaps that matter for a non-idempotent destructive write.

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?

A single sentence with the resource and its effect front-loaded; nothing is padded or redundant.

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 agent gets no hint of what is returned (e.g. a block id). For a six-parameter, non-idempotent, destructive write, the description should say more about side effects and reversibility, though the rich schema and annotations cover most of the structural surface.

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 the schema already carries all parameter meaning including ISO 8601 formats, the day-boundary rule on end_at, and the allow_online_booking default. The description adds no parameter detail beyond that, so the baseline 3 applies.

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 states a specific verb (block) plus resource (a time slot on a team member's calendar) and the concrete effect ('so nobody books it'). It implicitly separates itself from create_appointment, but it never names that sibling, so the differentiation falls short of a 5.

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?

The purpose phrase 'so nobody books it' implies the use case (reserving unavailable time), but there is no explicit when-to-use, when-not-to-use, or named alternative such as create_appointment or find_available_slots. An agent must infer the routing decision from context.

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