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

Annotations already declare readOnlyHint=true and destructiveHint=false, but the description adds substantial behavioral context beyond them: live operator settings are consulted, after-hours results may carry a surcharge, same-day requires a phone call, and the operator confirms every booking. These are operational nuances an agent cannot infer from annotations alone.

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?

The scoping constraint ('not prices') is front-loaded in the first clause, followed by the mechanism, edge-case behavior, and a final clarifying exclusion. Dense but every sentence adds decision-relevant information; 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?

With an output schema present, return values need not be explained, and annotations cover safety. The description still supplies everything needed to call correctly: what is checked, what is not checked (prices, driver calendar), the after-hours path, same-day handling, and the confirmation model.

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% (date as YYYY-MM-DD, time as HH:MM 24h, vehicle with enum-like values), so the schema carries parameter meaning. The description adds only light context ('optionally per vehicle' — checks that vehicle's days off), which largely restates the schema's vehicle description. Baseline 3 is appropriate.

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 precise verb+resource ('check availability') and immediately scopes it to 'Date/time bookability only — not prices', explicitly naming the sibling get_quote for fares. It also clarifies the domain (operator live settings: after-hours, days off, blocked dates, optionally per vehicle), so an agent can distinguish it from get_quote, get_service_info, and request_booking without opening any 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?

Gives explicit routing: use get_quote for fares, phone for same-day, and notes that outside-hours times are still bookable as after-hours requests (surcharge may apply). It also excludes a plausible misread ('not a driver calendar') and states that the operator confirms every booking, so the agent knows this is an inquiry, not a reservation.

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