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

Annotations already declare idempotentHint=true, destructiveHint=true and openWorldHint=true; the description reinforces these with concrete semantics ('repeating the same call returns the same booking, never a second one' and 'can't be cancelled or changed online'). It adds the real-world side effects (salon holds the time, customer receives a confirmation text) that the annotations cannot express, though it says nothing about permissions, failure modes, or rate limits.

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?

Four short sentences, front-loaded with the core action and then the consequences; each sentence carries weight. The opening 'Books an appointment' largely restates the title, which is the only wasted line.

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 no-output-schema, six-parameter mutation tool, the description covers the side effects (confirmation text, held slot) and idempotent behavior an agent needs to act safely. It does not say what the response contains (e.g. a booking identifier), which leaves a minor gap, but nothing critical 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 all six parameters are already documented in the schema, and the description adds no parameter-level meaning (it never explains slug, service_id, start_at format, or the agent_name visibility). Baseline 3 is appropriate when the schema does the work.

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 ('Books an appointment') and adds the essential nature of the operation: real, immediate, holds the slot, sends a confirmation text. It never names the sibling tools (check_availability, find_salons) or explicitly says the slot must be verified first, so it is clear but not fully differentiated.

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?

Usage context is implied rather than stated: the caller learns the booking is irreversible online and can only be undone by phone, which nudges toward caution, and start_at being 'an open slot' implies availability must be checked first, but no alternative tool is named and no explicit 'call check_availability before this' instruction appears.

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