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

Annotations cover the safety profile (readOnlyHint=true), so the bar is lower, and the description adds real value by disclosing the shape of the response: the affiliate's campaign, links, coupon, and visitor/lead/conversion counts, plus the underlying endpoint. It doesn't cover not-found behavior, but that is a minor gap for a read-only getter.

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 tight sentences: the core action and returned fields come first, with the API endpoint reference trailing as supporting detail. No filler, nothing repeated from the title or schema.

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 one-parameter read-only getter with no output schema, the description is nearly complete: it names the entity, the identifier type, and the main fields returned. Only edge behavior (missing id, error response) is left unstated, which is acceptable at this complexity.

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% and the single parameter is fully documented as a UUID in the schema, so the baseline is 3. The description only reinforces 'by id' without adding format, validation, or alternate-lookup guidance.

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 ('Fetch'), resource ('a single affiliate'), and scope ('by id'), which cleanly separates it from rewardful_list_affiliates and from the narrower get_affiliate_coupon / get_affiliate_link siblings. An agent can distinguish it without opening a schema.

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 'by id' framing implies the precondition (you must already have an affiliate id) and the lookup intent, but the description names no alternatives and gives no explicit when-to-use versus list_affiliates for discovering ids. Usage is inferable, not stated.

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