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

The readOnlyHint annotation already declares the safe-read profile, so the description's burden is lower, but it adds little beyond that: only the raw REST mapping (GET /v1/affiliate_coupons/:id). It says nothing about not-found/error behavior, whether the id must belong to the caller's account, or any rate limiting.

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, front-loaded with the action and followed by the endpoint mapping. Nothing is padded and no sentence is wasted.

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 single-parameter read tool with no output schema and annotations covering the safety profile, the definition is close to sufficient. The only genuine gap is error/not-found behavior, which is minor for this operation.

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 100%, with coupon_id documented as a UUID, so the schema carries the parameter meaning. The phrase "by id" corroborates but adds no new syntax, format, or lookup guidance beyond what the schema already states; baseline 3 applies.

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+resource pair (fetch a single affiliate coupon) and scopes it to one record by id, which implicitly separates it from the sibling rewardful_list_affiliate_coupons. It stops short of explicitly naming that sibling or the other get_* tools, so differentiation is inferable rather than stated.

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?

"By id" implies the precondition that the caller already holds a coupon id, which is the only real usage signal. There is no explicit when-to-use/when-not statement and no pointer to rewardful_list_affiliate_coupons for the case where only an affiliate is known, so guidance is implied at best.

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