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

Adds real context beyond the annotations: the server validates the slot first and the booking lands in a pending owner-approval state rather than being confirmed. That is a meaningful workflow trait not encoded in the destructiveHint/idempotentHint flags. It stops short of saying what happens when the slot is taken or what is returned.

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 short sentences, the core action first and the two behavioral caveats after. No filler, no repetition 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?

Annotations and schema carry most of the load, but for a non-idempotent, destructive mutation with no output schema, the description never says what a successful call returns (an appointment id?) or what failure looks like. The approval-state note is helpful but leaves the agent without the full picture.

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 explains note, dry_run, staff_id defaults, timezone handling and notify_client. The description only restates the required trio ('one service at a start time') and adds no semantics beyond the schema, so baseline 3 applies.

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?

Names a specific verb ('Book') and resource ('appointment' implied by the tool name), plus the scope: one client, one service, one start time. It implicitly separates itself from cancel_appointment/reschedule_appointment, but never names a sibling explicitly.

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 clause 'Booksy checks the slot first' implies this is the tool for attempting a booking rather than pre-checking, but it never points at find_open_slots for availability or mentions the dry_run parameter as the validate-only path. Usage is implied, not stated.

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