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

Annotations already declare readOnlyHint=false, destructiveHint=true, idempotentHint=true and openWorldHint=true; the description's main contribution is the 'WRITE:' prefix plus the notes-replacement semantics, which largely restate the schema. It does not explain the destructive aspect (overwriting existing notes), whether omitted fields are left untouched, or what is returned – gaps the annotations alone cannot fill.

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 short sentences with the 'WRITE:' safety signal and the resource scope front-loaded, then identifier semantics, then the endpoint. The parenthetical re-listing of the four status values is mildly redundant with the schema enum.

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 small 4-parameter mutation with no output schema, the description covers the operation, the identifier source, and the endpoint. What remains unstated – return payload and behavior of omitted fields – is minor but not trivial for a destructive, idempotent write.

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 75%, so the baseline is 3. The description explains customer_booking_id and enumerates the status values, but both facts are already in the schema and enum, so it adds no new semantics beyond structured fields.

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: set the arrival status and/or notes of one customer on a booking, and gives the exact endpoint PUT /bookings/{booking_id}/customers/{customer_booking_id}. The scoping phrase 'one customer on a booking' lets an agent separate it from the broader update_booking and the global update_customer siblings.

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?

'set the arrival status ... and/or notes' clearly frames this as a partial update where at least one field is supplied, and the endpoint anchors it to a booking-scoped customer record. There is no explicit when-not-to-use note (e.g. 'use update_customer for the customer's global record'), so routing to the closest sibling still needs inference.

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