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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint, so the safety profile is covered. The description adds genuinely new context beyond that: the $0.01 USDC x402 payment cost and the metering model, which matters for an agent deciding whether to call. It does not cover error behavior for invalid ZIPs.

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 tight sentences: what it returns first, then use cases, then cost. No filler, and the highest-value information is front-loaded.

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?

No output schema exists, so the description correctly takes on the burden of enumerating return fields, and it does so completely. For a one-parameter read-only lookup with annotations and a schema-declared param, nothing an agent needs to call it correctly is missing.

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 100% and the single parameter is documented in the schema with an example ('43210'). The description only restates '5-digit ZIP code', adding no format constraints or edge-case handling beyond the schema. Baseline 3 applies.

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?

Specific verb and resource ('US ZIP code lookup') followed by an explicit enumeration of returned fields (city, state, county, time zone, area codes, lat/long). Clearly distinguishable from siblings like interzoid_city_standard or interzoid_state_abbreviation.

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?

Names four concrete use cases (address validation, geocoding, territory mapping, form autofill), which gives a clear selection context. However, it never names an alternative sibling or an exclusion — e.g., it does not say when to prefer interzoid_address_parse or interzoid_global_address_match instead.

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