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

Annotations declare a non-readonly, non-destructive, non-idempotent write, and the description adds the important behavioral fact that omitted fields are prefilled from the account for signed-in customers, plus the hard requirement of name and email to issue a booking. It does not state whether a second call replaces or merges prior values, which matters given idempotentHint=false.

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?

Three tight sentences, front-loaded with what the tool does, then the requirement, then the call-ordering rule. No filler or restatement of the name/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?

With no annotations covering return behavior and no output schema, the description handles the important operational context: prerequisites, ordering relative to checkout, and prefill behavior. The required-vs-optional mismatch with the schema leaves a small ambiguity about whether the call can actually succeed with only session_key.

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 coverage is 100%, so the baseline is 3 and the schema already documents each field's meaning. The description adds useful override/prefill semantics for first_name, surname, and email, but it conflicts with the schema, which marks all three as required while the description says they may be omitted and prefilled.

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: attach the lead guest's contact details to the live booking cart. This clearly distinguishes it from bk_cart_add, bk_cart_promo, and bk_cart_checkout without opening any 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?

Gives explicit sequencing ('call once the cart has items and before bk_cart_checkout') and states the two invocation modes: call with just session_key for a signed-in customer, or pass explicit values to override. The condition that selects each behavior is spelled out.

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