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

Annotations already mark it as destructive and not read-only; the description adds the important clearing behavior (cost 0 clears) and discloses the confirmation payload (brand, title, price/price range, fulfillment). This goes beyond the structured annotations and gives useful behavioral context.

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 dense but efficient: purpose first, then trigger phrases, then the clear-by-zero edge case. It earns its length by covering behavior and usage that are not present in the schema, though the first sentence is a bit long.

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 simple setter with no output schema, the description covers why the tool exists, how to invoke it, what the confirmation echoes, and how to clear a value. Minor missing context like overwriting an existing value is not a serious gap given the destructive annotation.

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 schema already documents asin, cost_floor, and marketplace_id. The description reinforces that cost_floor is a landed unit cost and that 0 clears it, but adds little parameter-level meaning 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 states a specific verb ('Record'), a specific resource ('the user's cost basis for an ASIN'), and a concrete downstream purpose ('later checks can flag when the buy box drops below their cost'). This clearly separates it from the analytic and watchlist sibling tools, which do not write cost-basis data.

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 explicit trigger phrases ('my cost on B0... is $12', 'set my cost basis', 'I pay $X for this') and a clear one-ASIN-per-call rule. It does not explicitly state when not to use the tool or name alternatives, but no close alternative exists among the siblings.

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