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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so the safety profile is covered. The description adds genuinely new behavioral context: results are read live from the A2A Grocery source, implying freshness/no caching. It could say more about rate limits or failure modes when no listing exists.

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?

Front-loaded with the core check, then the payoff, then the data source — no padding. The phrasing is metaphor-heavy ("on the shelf", "A2A Grocery door"), which is compact but slightly informal for a precise lookup tool.

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 explained, and annotations carry the safety profile. What remains, the purpose and the live-data source, is stated. Format expectations for the three required identifiers are the only real gap.

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% across three required parameters, so the description must compensate. It does map the three concepts (GTIN, banner, market≈country_iso), but gives no format guidance for any of them, leaving syntax entirely to inference.

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 states a concrete question ("does the grocery record list this GTIN at this banner in this market?") that precisely defines the eligibility check and its scope. It is distinguishable from siblings like resolve_gtin (identifier lookup) or find_buyer, though it never names an alternative explicitly.

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 phrase "No listing, no media pitch" implies when the check matters (as a gate before pitching media), which is useful implied guidance. However there is no explicit when-to-use/when-not-to-use statement and no routing to alternatives such as resolve_gtin for pre-resolution.

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