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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is fully covered. The description adds the marketplace-scoping constraint and the prerequisite that the id comes from list_my_marketplaces, but says nothing about return shape, pagination, or freshness of the age data.

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 sentences, zero waste: purpose and scope first, user-intent triggers second, prerequisite last. The front-loading lets an agent decide relevance from the opening clause alone.

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 sketching what the tool returns (age-bucket distribution plus at-risk SKUs) and by stating the prerequisite id source. The main residual gap is the absence of any note on data freshness or how age buckets are defined.

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%, and the schema already explains both the marketplace_id source and the agency/account-omission refusal behavior in detail. The description merely restates that a marketplace id is required, adding no syntax or semantics beyond the schema.

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+resource ('FBA inventory age') and narrows the scope to one marketplace on the connected seller account, including the two outputs it produces (age-bucket distribution and SKUs nearing long-term storage fees). That scope is distinctive enough to separate it from get_stock_history or get_reorder_plan, though no sibling is named explicitly.

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 concrete user-intent triggers — 'is my stock getting old' and 'will I be charged storage fees' — which is clear when-to-use context. It does not name alternatives or state when not to use it (e.g. versus get_stock_history), so it stops short of full routing guidance.

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