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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered; the description adds genuinely new behavior: the data is read live from the calendar rather than cached, and returned times are timezone-local ISO 8601. It stops short of describing result shape (flat slot list vs. grouped by day) or any rate/expiry limits on the returned slots.

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, each carrying distinct information: what is returned, how to narrow the range, and how to consume the output. The core purpose is front-loaded with no filler.

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?

There is no output schema, so the description reasonably explains the return semantics (ISO 8601, business time zone, feed directly into book_appointment). It is nearly complete for a simple read tool; only the precise structure of the returned availability payload is unstated.

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?

With 0% schema description coverage the description must carry the parameters, and it does explain start_date as YYYY-MM-DD and days as 1-30, plus the implicit constraint that business_id must refer to a bookable business. However, the default of 14 days and the meaning of a null start_date are never mentioned, so the compensation is partial.

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 ('Open times for a business ... read live from its calendar') and scopes the input set to businesses that have can_book. It is clearly distinguishable from book_appointment and get_business, the tool an agent might otherwise confuse it with.

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?

Names the downstream step explicitly — 'pass one back unchanged to book_appointment' — which tells the agent this is the discovery half of a booking flow. It also implies a precondition (business must have can_book), but gives no explicit when-not case or alternative source for availability.

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