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

Annotations already declare readOnly, idempotent and non-destructive, so the safety profile is covered. The description adds 'Read live from the CPG Knowledge Graph door', indicating fresh live data rather than a cache, which is genuine extra context but shallow.

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 tight sentences with the core question front-loaded, followed by exclusions and the data-source note. The metaphorical phrasing ('on the shelf', 'door') is flavor rather than wasteful, but not fully austere.

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 an output schema present, return values need no explanation, and annotations cover the safety profile. What remains is a slightly under-specified notion of what 'eligible' resolves to, but the essentials for calling a 3-param read tool are present.

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%, so the description must compensate. It informally names all three concepts (GTIN, banner, market ≈ country_iso), giving partial mapping, but supplies no format or syntax for the codes and never explicitly ties 'market' to country_iso.

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 check — eligibility of a GTIN at a banner in a market — and explicitly contrasts it against adjacent work ('No listing, no media pitch'). It reads as a read-only eligibility probe. The metaphor ('on the shelf', 'Knowledge Graph door') and lack of explicit differentiation from resolve_gtin keep it from a 5.

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 listing, no media pitch' tells the agent what this tool is not for, which is useful negative guidance. However, it never states when to reach for check_eligibility over resolve_gtin or get_banner_card, leaving the choice to inference.

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