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

Annotations already declare read-only, idempotent, non-destructive, closed-world behavior, so the bar is lower. The description adds real value beyond that: ZIP boundaries and response-time estimates are not published, and an unknown result is not a denial — important interpretive context. It stops short of describing error behavior or coverage granularity.

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?

Three compact sentences with the core action front-loaded and no wasted filler. The final clause about the EntityGraph city-guide list is slightly jargon-heavy but still informative.

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 results, and it does so reasonably: hinting at coverage data, the city-guide list, and the unknown-vs-denied distinction. Minor gaps remain around response shape and error cases, but the agent has enough to call 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?

Schema description coverage is 0% for the single zipCode parameter, so the description must compensate. 'Check a US ZIP' clarifies the parameter is a US ZIP code, adding meaning beyond the bare ^\d{5}$ pattern constraint, though it omits explicit format or normalization 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?

States a specific verb and resource ('Check a US ZIP against available public coverage data'), which is concrete and clearly distinct from the sibling tools (pricing, offers, services, credentials). It does not explicitly name a sibling, but the coverage-domain purpose is unambiguous.

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 description implies its usage (coverage lookup for a ZIP) but gives no explicit when-to-use or when-not-to-use guidance. The caveat 'unknown is not a coverage denial' helps interpret results but does not route the agent between alternatives.

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