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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds genuinely useful behavior beyond that: no browser required, multi-format extraction fallback chain, missing facts returned as null, and a $0.002 per-result cost. The cost and null semantics are meaningful additions, but return shape and fetch-failure behavior are left to the output schema.

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 what is extracted and from where, then the routing/guardrail sentence. No filler and nothing repeated from the title.

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 described. Between the extraction sources, null-on-missing behavior, per-result pricing, and the named alternatives, an agent has everything needed to decide and invoke correctly.

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 both parameters are already documented in the schema; the baseline of 3 applies. The description reinforces the single-URL, product-detail-page constraint (not a homepage, not a batch), which is a mild addition over the schema rather than new syntax or format guidance.

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?

Specific verb+resource ('Product page to JSON') with the exact fields extracted (price, stock, variants, ratings, shipping) and the extraction sources named. It also distinguishes itself from the two nearest siblings by name, so an agent can route without opening 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?

States the positive case explicitly ('Use for one product detail URL') and then names two concrete alternatives with the conditions that select them: cross-store comparison and store-wide discovery audit. When-to-use and when-not-to-use are both covered.

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