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

Annotations already declare readOnlyHint, idempotentHint, and non-destructive behavior, so the safety profile is fully covered by structured data. The description adds no further behavioral detail (no pagination, result caps, or failure modes beyond what the schema documents), but it does justify the read with a concrete downstream use. With annotations carrying the behavioral load, a 3 is appropriate.

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 returned resource and payload, then the call-condition. The first sentence is a dense field list but every field earns its place by defining the tool's output surface (there is no output schema). Minimal waste.

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 by enumerating the metrics and ids returned. Combined with the schema's currency-scoping warning and the marketplace note, an agent has enough to call it correctly. It stops short of explicitly naming the sibling alternative, which is the only meaningful gap.

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%: the descriptions for days, limit, and marketplace_id already document defaults, the max-90 cap, spend-ordering, and the currency-scoping caveat. The tool description adds nothing parameter-specific, so the baseline 3 for schema-driven parameters is correct.

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 the exact resource (keyword and product ad targets) and enumerates the distinguishing payload (Amazon target ids, current bid, ad group/campaign ids, clicks, orders, spend, sales), which cleanly separates it from campaign-level siblings like get_ads_campaigns and search-term siblings like get_ads_search_terms. An agent can identify what this returns without opening the 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?

It gives an explicit trigger condition with rationale: 'Call this before proposing a bid change,' tied to the business reason (pricing a proposal against the seller's own break-even CPC). It does not, however, contrast itself against adjacent tools such as get_amazon_bid_recommendations or get_ads_negatives, so the when-not guidance is absent.

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