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

With zero annotations, the description carries the full burden and does so well: it discloses the billed cost ($0.03 USDC/call), the payment protocol and chain (x402, eip155:8453), robots.txt compliance, and the failure contract (blocked or unpriced pages return 'unavailable' and are not charged). Those are exactly the operational facts an agent needs before spending money on a call.

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 dense sentences with no filler; every clause carries information (cost, protocol, extraction sources, failure behavior). The billing banner leads ahead of the purpose statement, which is slightly less ideal front-loading, but the purpose is still established in the first sentence.

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 one-parameter, no-output-schema tool with no annotations, the description covers what is returned in substance (price, currency, availability, seller), what sources it reads, and what happens when it cannot price the page. Only minor gaps remain: exact response shape and whether 'unavailable' still bills partially are not spelled out.

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% and the single required parameter includes a concrete example URL, so the schema already does the heavy lifting. The description confirms the input is a product page URL but adds no format, normalization, or accepted-domain guidance beyond that. Baseline 3 applies.

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 uses a specific verb set (verified price, currency, availability, seller) against a clearly bounded resource (a product page URL), and names the extraction sources (JSON-LD / microdata / OpenGraph). This is far more than a restatement of the name. It falls short of a 5 because it does not distinguish itself from the sibling 'pricing' or 'pre_purchase_check' tools, which plausibly overlap.

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?

Usage is implied rather than stated: the tool takes a product page URL and returns verified commercial facts, so an agent can infer it is for product-level price checking. There is no explicit when-to-use/when-not, and no routing to or away from the sibling 'pricing', 'pre_purchase_check', or 'seller_reputation' tools despite obvious overlap.

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