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

Annotations already cover read-only, non-destructive and closed-world, so the bar is lower. The description adds real business behavior beyond them: the booking window, minimum lead time, business hours, and that time_zone only affects presentation, not availability.

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, front-loaded with what is returned, followed by constraints and the handoff to book_call. No filler and nothing repeated from the schema verbatim.

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?

With no output schema, the description does the necessary work of explaining what a result looks like (an exact start token for book_call) and what constrains the set. Only the shape of the returned list and empty-result behavior are left unstated, which is minor for a two-optional-param read tool.

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. The description goes further by clarifying that time_zone is for displaying times in the user's zone (not filtering them) and by reinforcing the two-week bound on from_date.

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: returns Nikita Marushkov's open times for a 30-minute Google Meet call. It also scopes the output (exact start times) and distinguishes itself from the sibling book_call, which consumes those times.

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 flow is clear: call this first, then pass an exact start to book_call. Eligibility constraints (Mon–Fri, 10–6 ET, last call 5 PM, 4 hours ahead, two weeks out) tell the agent when results will and won't exist, though there's no explicit 'do not use this to book' exclusion.

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