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

The annotations already declare readOnlyHint, idempotentHint, and destructiveHint, and the description adds meaningful behavioral context: it returns an error for a nonexistent id, rates are refreshed several times a day, and cashback is only credited when the user clicks the url link. This goes beyond the structured hints and is not contradictory.

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?

The description is appropriately sized and front-loaded: the core behavior appears first, followed by routing guidance, error/freshness information, and presentation instructions. Each sentence carries distinct, useful information with no filler or redundancy.

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?

Given the tool has a single well-described parameter, a read-only/idempotent annotation set, an output schema, and clear sibling alternatives, the description fully covers what the agent needs: when to call it, when not to, what to expect, and how to present results. Nothing material is missing.

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%, so the parameter is already fully documented in the input schema. The tool description reaffirms that store_id is numeric and should come from an earlier result, but does not significantly extend what the schema already states; hence baseline 3 is appropriate.

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 states a specific verb ('Returns') and resource ('current online and in-store cashback rates from every cashback portal for one store identified by its numeric store_id'), making the tool's purpose immediately clear. It also differentiates from the sibling by explaining the store_id vs store_name lookup split.

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 description gives explicit usage guidance: use only when a store_id is already known, and when only a store name is available, call get_cashback_rates_by_store_name directly without looking up the id first. This clearly routes the agent between two similar siblings and prevents unnecessary lookup steps.

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