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

Annotations already declare readOnly/idempotent/non-destructive, so the description earns credit for adding what they cannot: results are in the business's local time zone and are volatile ('times change as people book'). It does not describe output shape, but with no output schema this is a minor gap given the volatility warning is the key behavioral risk.

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 short sentences with the resource and scope front-loaded, followed by dependency guidance and then a freshness caveat. No sentence is redundant and nothing important 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 5-parameter read with no output schema, the description covers what is returned (start times), where the identifiers come from, the time-zone semantics, and result volatility. Only the exact return format (e.g., list of timestamp strings vs objects) is left 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?

Schema description coverage is 100%, so the schema already documents date format, days range, business id derivation, and professional_id. The description only restates optionality and adds the local-time-zone framing for dates, which is a small increment over the structured fields.

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 ('free start times for one service') plus scope qualifiers: single service, business local time zone, bounded horizon. It is clearly distinguishable from get_services (ids) and get_booking_link (booking), so an agent can pick it without opening the 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?

Explicitly routes the agent to get_services for the service_id and notes that a professional filter is optional. The closing sentence about the booking link hints at get_booking_link for live times but never states the when-to-use condition for that alternative, so the routing is clear but not fully spelled out.

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