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

Annotations already declare the mutation profile (readOnlyHint=false, destructiveHint=true, idempotentHint=false), so the safety burden is partly carried there. The description adds genuinely new context the annotations lack: plan-type restriction, buyer-only authorization scope, and a required active API key. It does not mention billing/cost impact or what the response returns, which would be desirable for a quantity-raising action.

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, front-loading the action, then the eligibility constraints, then the auth requirement. Every sentence adds a distinct constraint; there is no filler or repetition.

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 zero-parameter, no-output-schema tool, the description covers what it does, who may call it, and what credential is needed, which is sufficient to invoke it correctly. It omits any note on the resulting state change (proration, billing effect, confirmation of new seat count), which would round out the picture for a destructive, non-idempotent action.

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 tool takes zero parameters, which is the baseline-4 case per the rubric. Nothing in the description needs to compensate for schema gaps, and the schema is fully described.

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: 'Raises the Seat quantity on this subscription.' An agent knows this is a seat-quantity increment, not a configuration change. It does not name or contrast with the obvious sibling release_seat, which is the natural inverse operation, so it stops short of full sibling differentiation.

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 concrete applicability conditions: 'Seat plans only, buyer only. Requires an active Whimbrel key.' These act as exclusions that tell the agent when the tool does and does not apply. No explicit routing to an alternative (e.g., release_seat for decreases) is provided.

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