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

Annotations already declare readOnly hint, so the bar is lower; the description nevertheless adds ordering (newest first), the returned metrics, the zero-or-one semantics of the lookup filters, and that campaign/links/commission_stats can be expanded for depth.

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 tight clauses front-loaded with what/ordering, then filter modes, then expansion, closing with the underlying endpoint. 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?

With no output schema, the description usefully describes the returned fields and the zero-or-one case. It leaves pagination behavior and the default page size to the schema, which is acceptable but not fully complete for an agent unfamiliar with the endpoint.

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 coverage is 100%, so every parameter is already documented in the schema; the description only echoes campaign, email, stripe customer id, and expand without adding format or default detail beyond what the schema provides. 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 and resource (list affiliates) plus what each row carries (visitors/leads/conversions) and the ordering (newest first). This differentiates it from the singular rewardful_get_affiliate and from the other list_* siblings by naming its own filter modes.

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 clear selection context: filter by campaign for a set, or use email/stripe_customer_id to resolve a single affiliate (returns zero or one). It never names get_affiliate as the alternative for a known id, so it stops short of explicit when-not guidance.

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