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

Annotations only declare readOnly/openWorld, which is a low bar; the description goes well beyond by disclosing the paid-metering model: $0.002 in USDC per successful call, payable via x402 on Base, Solana or Arc, with failed calls not charged. That billing-on-failure detail is exactly the kind of behavioral trait an agent needs before calling, and it is not derivable from any structured field.

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?

Three tight sentences: purpose first, scope exclusions second, cost model last. Every clause carries information an agent would otherwise have to guess, and there is no padding or restatement of the tool name.

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 an output schema present and 100% parameter coverage, the description only needs to carry scope, exclusions and cost — all three are covered. Nothing needed for correct invocation is missing.

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 coverage is already 100%, so the baseline is 3, but the description earns more by clarifying that matching runs against recall date and description text and, for FDA, the reason-for-recall field. It still doesn't clarify whether `days` applies to both sources or only CPSC, which the schema hints at but leaves ambiguous.

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 and resource ('Recent US recalls matching a keyword') and then itemizes the exact data sources it draws from: CPSC consumer-product recalls and FDA food enforcement reports. It explicitly names what is out of scope (NHTSA vehicle, FDA drug/device), so an agent can tell at a glance whether this tool covers its need.

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?

The exclusion list ('Vehicle (NHTSA) and FDA drug/device recalls are not included') gives clear negative routing guidance, and the keyword-driven scope is stated up front. It does not name an alternative tool to use for the excluded recall classes, so it stops short of full when/when-not routing.

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