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

Annotations already cover readOnly/idempotent/openWorld/non-destructive, so the bar is met; the description adds genuinely useful behavior beyond them — the call is public, a logged-in session returns "my" entries, and an empty result is normal and must not be padded with external reviews. These are real operating nuances not captured by annotations.

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?

Extremely dense and front-loaded: scope, auth behavior, empty-result caveat, sibling exclusion and the write alternative all fit in a few clauses. Slightly telegraphic wording costs it a point but nothing 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 read-only tool with no output schema, the description conveys the shape of the return (distribution/total/reviews), auth-dependent scope, and the correct sibling for the write path. Enough to call it correctly; only the overlap with get_product_rating_summary is left unaddressed.

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 sort/limit/cursor/productId are already documented in the schema. The description adds no parameter-level syntax or format detail, so the 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?

The description names a specific verb and resource: reading a product's rating distribution, total count and reviews, and explicitly distinguishes it from get_product ("get_product不含此表"). It is clear what the tool returns, though it never distinguishes itself from the sibling get_product_rating_summary, which handles a very similar summary surface.

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 routes the agent away from the wrong sibling for writes ("写评用rate_product") and clarifies that the rating table is not obtained via get_product. It also states that logged-in calls additionally include the caller's own data ("登录含my"). No explicit when-not/when guidance beyond these, so a 4 rather than 5.

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