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

Annotations already declare readOnlyHint=true, idempotentHint=true and destructiveHint=false, so the safety profile is covered. The description adds genuinely useful context beyond that: the tool returns a booking link, a human must confirm with name and email, and no booking or charge occurs — clarifying the human-in-the-loop and side-effect-free nature.

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?

Two sentences, fully front-loaded, with no filler. The most important fact — that this only produces a link and nothing is booked — is placed last for emphasis without padding.

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 4-parameter tool with full schema coverage and no output schema, the description covers purpose, the human confirmation flow, and what is returned (a link). An agent has everything needed to select and invoke it 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 description coverage is 100%, so each parameter (gym, date, class_id, locale) is already documented in the schema and the baseline is 3. The description only alludes to 'optionally the class already picked', adding no syntax or format detail beyond 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 ('Gives the link to book a trial class at a Gymmy gym') and scopes exactly what is produced. The closing clause ('nothing is booked or charged by this tool') distinguishes it from the sibling book_class, so an agent can route correctly without opening either 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?

Clearly frames the tool as the pre-booking step: it returns a link the person opens and confirms with name and email, and nothing is booked or charged. This makes the boundary with book_class inferable, but the sibling is never named and no explicit 'use this instead of X when Y' guidance is given.

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