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

Annotations already declare readOnlyHint, openWorldHint, and idempotentHint, covering safety and idempotency. The description adds meaningful context about access control: the booking must be owned by the supplied user_key, which is not conveyed by 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?

A single, front-loaded sentence of 9 words. No wasted words, and every word adds value: 'Query a booking' states the action, 'owned by the user_key account' clarifies scope.

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 is simple with two well-documented parameters, an output schema, and annotations covering read-only/idempotent behavior. The description is sufficient for correct invocation, though it does not mention behavior for missing bookings or invalid keys—acceptable given the output schema likely covers responses.

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 descriptions cover 100% of parameters, so baseline is 3. The description adds extra semantics by tying user_key to ownership ('owned by the user_key account'), which clarifies the relationship between the two parameters beyond their individual schema descriptions.

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 uses a specific verb ('Query') and resource ('a booking'), and adds scope ('owned by the user_key account'). This clearly distinguishes it from siblings like create_booking, cancel_booking, and query_room_rates.

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 clear context: it queries a booking linked to a specific user_key. It does not explicitly mention when not to use it or name alternatives, but the ownership scope and sibling names imply appropriate usage for read-only booking lookups.

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