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

Beyond the annotations (which only indicate non-read-only, non-idempotent), the description reveals key behaviors: omitted fields are prefilled from the customer's account, explicit values override, and the tool is a prerequisite for booking issuance. It adds meaningful context about the prefill/override mechanism, which is not obvious from the schema 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 concise and well-structured: it starts with the core purpose, then provides necessary context about Bookeasy's requirements and prefill behavior, and ends with precise usage timing. Every sentence contributes useful information without redundancy.

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?

The tool has no output schema, so the description does not need to explain return values. It covers the essential aspects: what the tool does, when to call it, and the prefill/override behavior. It could mention error cases or response content, but for a cart-attachment step the current description is sufficiently complete.

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% with descriptions for all five parameters. The description augments this by clarifying that first_name, surname, and email can be omitted for signed-in customers (prefilled from account), and that explicit values override prefilled ones. This adds value beyond the schema's basic field labels.

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 clearly states the tool's function: 'Attach the lead guest's contact details to the Bookeasy cart.' It specifies the resource (Bookeasy cart) and the specific action (attaching contact details), distinguishing it from sibling tools like bk_cart_add and bk_cart_checkout.

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 provides explicit timing guidance: 'Call once the cart has items and before bk_cart_checkout.' It also explains how the tool behaves for signed-in customers, giving a clear usage pattern (call with just session_key to confirm prefilled details or pass explicit values to override). It does not explicitly name alternatives but the workflow context is clear.

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