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

Annotations already declare readOnly/idempotent/openWorld, so the safety profile is covered. The description adds genuine value beyond them: the 'never invents missing fields' guarantee and the concrete auth/billing paths (x402 PAYMENT-SIGNATURE vs. Stripe headers). It does not cover caching/TTL behavior implied by max_age_ms or failure modes on non-product pages.

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 the core action; the dense payment clause is functional rather than filler. The billing detail is arguably over-specific for a tool description, but it is actionable and placed after the purpose.

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 no explanation, and the annotations plus auth notes cover the operational envelope. However, with 0% schema coverage the unexplained select/response_mode/max_age_ms parameters and the absent routing guidance leave real gaps for correct invocation.

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 0% and the description explains none of the four parameters. 'Selected product fields' loosely gestures at select, but max_age_ms (cache control) and response_mode (minimal/standard/evidence) are left entirely unexplained, forcing the agent to guess at their meaning and interaction.

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+resource: 'Extract selected product fields from a public product page.' An agent can distinguish this from compare_products or website_audit by the resource (a product page) and output (product fields). It stops short of explicitly naming which sibling to use instead for adjacent tasks.

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 or when-not-to-use guidance. Nothing says when to prefer this over web_qa, compare_products, or website_audit, nor what preconditions apply (e.g., page must be a public product page, not a listing page). The payment sentence addresses billing, not task selection.

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