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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), and the description adds real value by disclosing the derivation basis: working hours, bookings, blocks and time off. That tells the agent the result is a computed intersection, not a raw listing. Timezone handling and slot granularity remain unstated.

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 dense sentence with no filler, front-loading the resource and the one-day constraint. It is a fragment rather than a full clause, but nothing is wasted and nothing is buried.

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 four-parameter read-only lookup with full schema coverage and clear annotations, the description covers the essentials plus the data sources behind the result. The shape of the return value (plain times vs. times with staff) is not described and there is no output schema, which is the only notable gap.

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 all four parameters including defaults and the list_services reference are already documented in structured fields. The description only reinforces the single-day scope and adds no syntax or format detail beyond the schema, so 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?

States a specific verb-equivalent ('free start times') and resource (service availability on one day), which is clearly distinct from siblings such as list_appointments. It does not explicitly name a sibling, but the availability-search intent is unmistakable.

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?

Usage is only implied: an agent can infer this is the pre-booking availability check before create_appointment, but the description never says when to use it versus listing appointments or staff. No prerequisites or exclusions are stated.

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