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

No annotations are provided, so the description carries the full burden. It discloses one useful behavioral detail — 5 free trial calls per signed wallet — implying a metered, wallet-authenticated paid service. However, it omits what happens after the quota is exhausted, what the error/response looks like, and whether the call is read-only or stateful.

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?

A single front-loaded sentence that leads with the resource and states the outcome. The pricing emoji/free-trial clause is extra but short; nothing is padded or verbose.

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, no annotations, four undocumented parameters at 0% coverage, and zero required fields, the description should explain which input to supply and what is returned. It leaves the core input ambiguity unresolved, so an agent could easily call it with the wrong field.

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% and the description only names 'postal code and country', leaving three of four parameters (zip, code, input) undocumented aliases with no explanation of precedence or required relationships (schema marks zero required). The description does not compensate for the coverage gap.

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: 'Resolves a postal code and country to place names with state and coordinates.' That is far more informative than a tautology. It doesn't explicitly differentiate from near siblings like x402-validate-postal-code or x402-geocode, but the resolution scope is clear enough to distinguish the general intent.

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?

There is no when-to-use guidance, no prerequisites, and no alternative named. The only contextual sentence is about free trial quota, which is a billing fact rather than usage guidance. An agent gets no help deciding between this, x402-validate-postal-code, and x402-zip.

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