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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint, and destructiveHint=false, so the safety profile is covered. The description adds meaningful behavioral context by disclosing the per-call cost ($0.001 USDC) and the normalization/aggregation behavior, but omits rate limits or data freshness.

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?

A single front-loaded sentence with no filler, which is appropriately sized. The parenthetical cost is placed at the end, which is reasonable, though it slightly muddles the resource description.

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?

An output schema exists, so return values need not be explained, and annotations cover the safety profile. However, the description leaves the agent without usage guidance or any clarification of the UCP acronym/source, which is a notable gap for a tool with an obscure domain term.

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 query, inStockOnly, and maxPriceUSD are already documented in the schema. The description adds no parameter-level meaning beyond what structured fields provide, making the baseline 3 appropriate.

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 (aggregates and normalizes) and resource (UCP merchant product catalogs, prices, checkout URLs), so the agent understands this is a product/deal aggregation tool. It does not differentiate itself from potential siblings, though none of the listed siblings clearly overlap with shopping/deals search.

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?

No when-to-use guidance, no prerequisites, and no named alternatives are given. The only usage-relevant hint is the $0.001 USDC cost, which implies a paid call but does not tell the agent when to prefer this over data_feeds, public_data_feed, or web_scraper.

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