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

With no annotations and no output schema, the description carries the full burden of behavioral disclosure. It explains what it checks but not the return format (e.g., boolean vs result object), validation strictness, or whether it is a pure read-only operation.

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 short and front-loaded. The 'Is IP:' prefix is redundant but harmless, and the rest of the single sentence earns its place.

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 tool with an empty schema, no annotations, and no output schema, the description lacks critical invocation details and return-type information. It also fails to differentiate from closely related validators like x402-validate-ip.

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?

The input schema has zero properties, so baseline is 4, but the description's 'Provide value or input' is ambiguous about the actual parameter name and expected format. An agent cannot tell whether to send 'value', 'input', or some other field.

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 clear verb ('Check') and resource ('whether a string is a valid IPv4 or IPv6 address'). It conveys the combined IPv4/IPv6 scope, though it doesn't explicitly distinguish itself from x402-validate-ip or x402-is-ipv4/x402-is-ipv6.

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 guidance is given for when to use this tool versus close siblings like x402-validate-ip, x402-is-ipv4, or x402-is-ipv6. The phrase 'Provide value or input' hints at invocation but not selection criteria.

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