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

Annotations already declare readOnlyHint=false, destructiveHint=false and openWorldHint=true, and the description is consistent with all three. It adds real context beyond them: Booksy applies its own automatic confirmation, the client becomes part of the booking, per-call confirmation is on by default and can be disabled for this tool, and a Cotlet API key with app access is required.

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?

Purpose and the key input source are front-loaded, and sentences are short. A couple of clauses (default confirmation toggle, generic confirmation reminder) are somewhat boilerplate, but nothing is padded or ambiguous.

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 mutation tool with no output schema, the description covers the important gaps: external side effects (reaches other people), confirmation policy, and auth requirements. It leaves out what happens on conflicts (e.g. double-booking an occupied slot), which would round it out.

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 all five parameters including client_id, service_id, start and staff_id defaults. The description restates the shape of the call (one client, one service, one start) but adds no format or sourcing detail beyond pointing at find_open_slots, so the 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?

States a specific verb and resource ('Book a client into your calendar') plus the exact scope ('one client for one service at a start time'). It also names the sibling that supplies the required input ('Pick a start from find_open_slots'), so an agent can distinguish it from booksy_reschedule_appointment and booksy_list_appointments without opening the 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?

Explicitly routes the agent to booksy_find_open_slots for sourcing the start time and states the confirmation precondition ('confirm with the user before each call'). It does not, however, state when not to use this tool (e.g. use reschedule for existing appointments), so it falls short of the full when/when-not/alternatives bar.

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