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

With annotations already declaring readOnlyHint=true and destructiveHint=false, the description still adds real value: it says appointments, personal blocks and gap time are excluded, that results are ordered by start time, and that a Cotlet API key with app access is required. It omits timezone and slot format details, but the safety profile is well covered.

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?

It front-loads the core behavior, but the exclusion list ('after working hours, personal blocks and gap time' / 'Appointments, personal time blocks and gap time are taken out') is stated twice, and the trailing auth-key sentence reads like boilerplate.

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 read-only lookup with no output schema, the description covers what is returned (ordered start times), what is filtered out, the advisory nature of the result, and the auth requirement. Missing only low-level return details such as timezone or slot duration.

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 100%, so the baseline is 3, but the description adds meaning by explaining that slots must be free 'for the combined length of the services' — clarifying that multiple service_ids are summed rather than treated independently, which the schema does not state.

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 ('Open times for a service on your calendar') and what the result represents (free start times). It is clearly distinct from siblings like glossgenius_list_appointments or glossgenius_book_appointment, though it never names an alternative 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?

The caveat that GlossGenius can still book outside these times and the tool 'only suggests them' implies this is an advisory lookup to run before booking, but there is no explicit when-to-use/when-not statement or named sibling alternative.

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