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

Annotations already declare readOnlyHint and idempotentHint, so safety is covered; the description adds the important behavioral caveat that this is a stored snapshot rather than a live quote. It also discloses the temporal window (180 days) and that results are derived from recorded observations, which is genuine context beyond annotations. It stops short of describing data freshness or gaps in the recorded history.

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?

Two sentences, front-loaded with the resource and scope, then the return payload, then the key caveat and alternative. Every clause carries information an agent would otherwise have to infer; nothing is 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?

With no output schema, the description must convey return values, and it does so completely: current price, 180-day low/high/average, sample count, and relative position. Combined with annotations covering the read-only profile and the explicit alternative for live data, an agent has everything needed to call this correctly.

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?

There is one parameter, 'asin', with 0% schema description coverage, so the description carries the burden. It implies the asin identifies 'a product' but never states the format or that it is an Amazon ASIN, so compensation is only partial. 'asin' is a reasonably well-known identifier, which keeps this at an adequate rather than poor level.

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 with explicit scope: 'Get a product's 180-day price change summary from recorded history'. It also enumerates what the summary contains (current price, low/high/average, sample count, position), so an agent can distinguish it from get_price and scrap_page without opening any 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?

Gives a clear use case ('is now a good time to buy' style questions) and names the alternative explicitly by pointing to scrap_page for live prices, including the when-not-to-use condition (not real-time). It does not contrast against get_price, which appears to be the closest sibling for current pricing, leaving a small routing ambiguity.

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