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

Adds real behavioral context beyond the annotations: it explicitly states existing appointments are NOT cancelled and that the call reports overlaps, which is important given destructiveHint=false and idempotentHint=false (a repeat call may create another block). It does not discuss auth/permission requirements or whether the block is scoped to one calendar/provider.

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?

Two dense sentences; the core action and its parameter-driven variants are front-loaded, and the non-cancellation caveat follows immediately. No filler or restatement of the title.

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?

No output schema exists, but the description compensates by noting the call reports overlapping appointments. With 5 parameters at 80% coverage and one required field, the definition is nearly complete; only the `reason` parameter and auth expectations are unaddressed.

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 already 80%, but the description adds the combinatorial meaning the schema cannot: which parameters must be paired together for each blocking mode. The only gap is `reason`, which is undocumented in both the schema and the description, a minor omission for a non-required field.

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 ('block time so nothing can be booked in it') and decomposes the operation into three unambiguous modes (whole day, date range, partial day) keyed to parameter combinations. An agent can immediately tell this apart from browsing tools like find_open_times or the scheduling siblings, which all read or create bookings rather than reserve unbookable blocks.

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?

Clearly signals when each parameter combination applies (date alone vs. date+end_date vs. date+start+end), which is genuine usage guidance for choosing an invocation shape. It never names an alternative for the inverse operation — remove_time_off is the obvious counterpart and goes unmentioned — so sibling disambiguation is left implicit.

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