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

Beyond readOnlyHint/openWorldHint, it discloses that it reads only what the page publishes and that Merchant Center/Google decide eligibility for any Google feature — a real scope limitation an agent must know. It also previews the per-field verdict format and the buy-ability guess.

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?

Purpose is front-loaded in the first clause, with usage and limitations trailing in separate sentences. The parenthetical field list is long but each item is load-bearing for understanding what is validated; slight density is the only cost.

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 no output schema, the description carries the burden of explaining return values and does so (per-field present/missing/invalid with remediation, plus a purchase-ability guess). Combined with the eligibility caveat, an agent has everything needed to call and interpret it 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?

Only one parameter, fully documented in the schema (100% coverage), so baseline is 3. The description adds a mild constraint — one product URL per template, a live public page — but gives no format or validation detail beyond what the schema already says.

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 (checks) and a tightly scoped resource (one live product page's Product/ProductGroup/Offer structured data against Google's merchant-listing fields). The enumeration of validated fields makes it unmistakable versus siblings like mttr_schema_create or mttr_page, even without naming them.

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?

"Use it on one product URL per template before and after a fix" gives concrete operational context for when to call it. It stops short of explicit exclusions or naming an alternative tool for other page-checking needs, so it is clear but not fully routing.

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