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

Annotations already declare readOnlyHint=true, so the safety profile needs no restating. The description adds genuinely non-obvious behavior: the implicit one-year default window, the requirement that NPS mode reports promoters/passives/detractors, and the SKU requirement that only applies in product mode. It does not mention rate limits or pagination, but aggregates presumably return a single payload.

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 dense sentences, front-loaded with what is aggregated, followed by the mode enumeration and the default-window caveat. Nothing is wasted, though the mode list inside the first sentence makes it slightly unpacked.

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 compensates by naming what the response contains. With 14 parameters and 93% schema coverage, it correctly focuses on the one knob (mode) that changes the tool's behavior plus the important default. Filters like tags, media, and enhanced_insight are left entirely to the schema, which is acceptable but leaves a small gap for complex filtering scenarios.

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 93%, so the schema already documents nearly every parameter; the baseline is 3. The description still adds value by explaining the semantics of the mode enum (including what nps returns and the product-mode dependency) and by flagging the lifetime-vs-default choice for since_period, which the schema states but the combined guidance makes actionable.

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 opens with a specific verb and resource ('Aggregate ratings for your Feefo account') and enumerates the outputs (average rating, star distribution, merchant details, review counts). It is clear what the tool returns, but it never distinguishes itself from the sibling feefo_get_product_ratings, which appears to overlap for product-level aggregates.

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?

It gives a usable conditional rule ('mode=product needs product_sku or parent_product_sku') and warns that the Feefo default is the last year, pointing to since_period=all for lifetime figures. However, it does not say when to prefer this tool over feefo_get_product_ratings or feefo_list_reviews, so the agent gets context but no exclusions or alternatives.

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