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

Adds real context beyond the annotations: credit cost per successful call, the warning that repeated calls may charge again (consistent with idempotentHint=false), and a data-trust caution. Annotations already cover the read-only/safe profile, so this cost and trust guidance is a genuine value-add.

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?

Front-loads what is retrieved, then cost, then the trust caveat. Four short sentences with minimal waste, though 'default cost... actual cost follows your plan' is slightly redundant.

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 6-parameter read tool with full schema coverage and no output schema, the description covers purpose, cost, and data-trust sufficiently. It omits any hint of return shape or pagination, but the enumerated fields (price, rank, rating, snapshots) give a reasonable sense of the payload.

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 all six parameters; baseline is 3. The description adds nothing about startTimestamp/endTimestamp format or the meaning of dailyLatest, so it does not exceed the schema's contribution.

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 (retrieve) and resource (historical price, rank, rating, listing snapshots) tied to an ASIN. The word 'historical' distinguishes it from current-state siblings like amazon_asin_detail, but it never names or contrasts with those siblings 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?

Provides no when-to-use guidance and does not reference any of the many sibling tools (amazon_asin_detail, amazon_asin_sales_trend, amazon_asin_competitor). The only implicit signal is 'historical', leaving the agent to infer selection from the name alone.

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