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

With no annotations, the description carries the full burden and does substantive work: it discloses that unknown/ambiguous prices are reported rather than invented (anti-hallucination behavior), restricts usage to no polling/ordering, and discloses the $0.005 USDC on Base via x402 payment requirement, which is critical auth/cost context. It stops short of describing failure modes or what a partial extraction returns.

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?

Five short sentences, each load-bearing: core action first, then optional comparison, then the honesty guarantee, then usage limits, then cost. Zero filler and fully front-loaded.

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?

Given no output schema, no annotations, and a nested parameter object, the description supplies the essential missing pieces: extracted fields, comparison mode, ambiguity handling, usage restrictions, and payment. Only the shape of the returned snapshot and the nested status semantics are left for the agent to infer.

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 0% and one parameter is a nested object, so the description must compensate. It conveys the concept of both params (a product page URL and an optional caller-owned previous snapshot) and even echoes the 'ambiguous' status vocabulary, but gives no field-level guidance for the nested snapshot object (required url/status, additionalProperties false) or the URL constraints.

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 (Extract) and resource (server-declared product price, currency, stock availability) with a clear scope constraint: a single public product page. This cleanly separates it from siblings like canonical-crypto-spot-price, canonical-web-scrape, and web-reader without the agent needing to open 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?

The description defines usage boundaries: single page only, no unattended polling, no ordering, and an optional comparison mode against a caller-owned snapshot. It gives clear context but never names a sibling alternative for the adjacent cases (e.g. generic scraping or crypto pricing), so the when-to-use is implied rather than routed.

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