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 useful behavior: only open times are returned, results are ISO 8601 with offsets, the range cap, and the both-calendars intersection rule when windows are supplied.

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 sentences, tightly front-loaded with the scoping constraint (14 days) and the optional-parameter effect, and it closes with the return-format note. 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?

For a bounded search tool with no output schema, the description covers what it returns (ISO 8601 times with offsets), which times appear (only open, optionally intersected), and the range limits. Nothing needed for a correct call is missing.

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 from, to, items and windows in detail. The description restates the windows semantics (customer free time, fits both calendars) but adds no syntax or format meaning beyond the schema, matching the baseline 3.

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 ("Find the start times that are open") plus the relevant scope constraints (between two dates, at most 14 days). It never names a sibling, but the read-only availability lookup is naturally distinct from book/cancel_booking in the tool set.

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?

Gives a clear conditional for the optional parameter: pass `windows` to intersect with the customer's calendar, omit it to see every open start. No explicit when-not guidance or reference to the booking flow's alternatives, so it stops short of a 5.

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