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

Annotations already declare readOnlyHint=true, but the description adds non-obvious behavior: the API surface is POST yet the operation is read-only, and the returned period granularity varies (hour / quarter / half / day) based on the range and a system setting. It does not cover auth needs, rate limits, or result-size limits.

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?

Purpose and scope are front-loaded in the first clause; the em-dash aside listing returned arrays is dense but information-bearing, and the second sentence delivers the POST clarification crisply. Slightly long single sentence but no wasted filler.

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 carries the return-value burden and does so well by naming each returned array and the linked opportunities. It is thin only on error behavior, result limits, and how store_ids scopes the response.

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 the baseline is 3; the description still adds meaning by making the single-product constraint explicit and by tying starts_at plus days_period to the resulting period granularity — a behavior of the date-range pair the schema fields alone do not convey. It adds nothing further for store_ids.

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 ('Rental availability'), pins the scope to exactly ONE product over a date range, and enumerates the returned quantities — enough to separate it from sibling list tools like list_stock_levels and list_product_inventories 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?

Usage is implied by the single-product, date-range framing rather than stated: there is no explicit 'use this when... use X instead' guidance against the stock-level or product-inventory list tools. The 'Read-only, even though the API uses POST' note is useful context but is not usage routing.

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