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

Annotations already declare readOnlyHint=true, so the read-only nature is covered. The description adds valuable behavioral context: slots expire after ~15 minutes and are the only valid source of slot_id, which is critical for correct usage. It also warns against assuming availability, which is a caution beyond the annotations.

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 sentences with no wasted words. The first sentence front-loads the core purpose and conditions, and the second provides filter options and a critical expiration warning. It is concise and immediately scannable.

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?

While the description gives a good overview, it leaves gaps: it doesn't explicitly state that either quote_id or booking_reference is required, and session_id is completely unexplained. With no output schema, it also doesn't describe the return structure beyond mentioning slot_id and expiration. These are important for an agent to call correctly.

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 only 20% (only customer_grant has a description), so the description must compensate. It explains quote_id and booking_reference usage, and the 'wanted' filter types (asap, date, range, preferred) with optional part_of_day. However, it omits session_id and the date/time fields (from, to, preferred_time), relying on schema patterns instead.

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?

Description clearly states the tool returns 'real, currently bookable appointment slots' and differentiates between new bookings (quote_id) and rescheduling (booking_reference). It also emphasizes it's the 'only valid source of slot_id', making its role unmistakable among siblings like create_booking and reschedule_booking.

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?

Specifies when to use it: for a new booking with a quote_id, or for rescheduling with a booking_reference and customer_grant. It also strongly advises 'Never assume availability without calling this tool', which implies it should be called before any booking action. However, it doesn't explicitly name alternative tools or state when not to use it.

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