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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds the cost detail ($0.01 USDC via x402), which is a meaningful behavioral disclosure beyond the annotations. It also clarifies the output scope (city, state, county, timezone, area codes, lat/long), giving the agent a concrete expectation of what the call returns.

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?

The description is a single sentence that front-loads the core purpose and lists the return fields, followed by a concise cost note. Every word earns its place; there is no filler or repetition of the tool name.

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?

For a simple one-parameter read-only lookup with a fully documented schema and safety annotations, the description is nearly complete. It states the input format, the output fields, and the cost. The only minor gap is that it doesn't specify behavior for invalid or non-existent ZIP codes, but this is a small omission for a tool of this simplicity.

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%: the only parameter, 'zip', is described as 'US ZIP code (5-digit)' with an example. The description adds no new parameter semantics beyond what the schema already provides. Baseline 3 is appropriate because the schema fully documents the parameter.

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 specific verb ('Get') and resource ('detailed info for a US ZIP code') and enumerates the exact fields returned (city, state, county, timezone, area codes, lat/long). This clearly distinguishes it from sibling tools like interzoid_country_info or interzoid_state_abbreviation, which cover different geographic entities.

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 when to use it: when you need US ZIP code details. It does not explicitly state when not to use it or name alternatives (e.g., use interzoid_country_info for non-US locations). The context is clear enough for a single-purpose lookup tool, but there is no explicit exclusion or alternative routing.

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