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

Beyond the annotations, the description discloses that the booking is created as 'pending', that the business must still confirm it, that prepayment may require a payment link, and that the slot is not held indefinitely. This is valuable behavioral context not available 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 description is well organized with a clear WHEN TO USE section and a few focused caveats. It is slightly longer than necessary due to some repetition between the opening line and the usage section, but every sentence still earns its place.

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?

Given the tool has no output schema and 8 parameters, the description covers the key context an agent needs: prerequisites, required user input, pending status, prepayment behavior, and venue eligibility. Nothing critical is missing for correct invocation and user communication.

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?

The schema already documents all 8 parameters, so baseline is 3. The description adds useful context beyond the schema, such as the requirement that the contact must match where the code was sent, and reinforces that start_time must come from a check-availability slot.

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?

The description opens with a specific verb and resource ('Book a slot') and identifies the exact precondition (a code from request-booking-code). This clearly distinguishes it from sibling tools like check-availability and request-booking-code.

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 description explicitly states WHEN TO USE: it is the last step after the user has confirmed venue, service, and exact time and has provided the 6-digit code. It also gives important constraints like requiring the same contact the code was sent to and only working for venues with is_bookable: true.

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