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

The only behavioral claim, 'Read only,' merely restates readOnlyHint=true and destructiveHint=false already in the annotations, adding zero new information. Nothing is said about pagination, ordering, whether expired coupons are included, or what a returned coupon contains.

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?

Two short sentences, the resource front-loaded. The second sentence ('Read only') is redundant with the annotations and is the only wasted text, but the overall length is appropriate for a trivial read tool.

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 parameters, no output schema, and safety covered by annotations, the description is minimal but not obviously incomplete. It nonetheless leaves an agent unable to predict what a coupon object holds or whether plan association matters, which is the kind of context a description should supply when no output schema exists.

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, so there is nothing for the description to disambiguate; baseline 4 applies. The description correctly implies no filtering input is needed.

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 names the resource ('discount coupons for the trainer's plans') but is a bare noun phrase with no verb, so the listing/retrieval action only comes from the tool name. It is unambiguous enough because no sibling tool deals with coupons, but it does not state scope (all coupons? active only? by plan?).

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?

'Read only' describes safety, not when to call the tool. There is no guidance on when to use it versus e.g. get_subscription or list_subscriptions when an agent needs to know what a trainer's plans cost after discounts.

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