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

Adds critical behavioral context beyond the annotations, notably that classification requires no lookup and costs $0.001 in USDC on Base per successful call via x402. This explains the non-read-only payment side effect and sets cost expectations the annotations alone do not convey.

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 front-loaded with the core action and outputs, then adds a use case, then a payment note. All three sentences carry unique, useful information with no filler.

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 still lists the return fields an agent can expect: version, address class, and integer plus reverse-DNS forms. It also discloses the payment model, which is essential for correct invocation.

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 100%, and the schema only documents the parameter as 'The IP address.' The description improves on that by clarifying that both IPv4 and IPv6 inputs are accepted and that no lookup is performed.

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 ('Classify') and resource ('IPv4 or IPv6 address') and enumerates the exact classification outputs, including version, private/loopback/link-local/CGNAT/public, and integer/reverse-DNS forms. The scope 'without any lookup' also distinguishes it from lookup-based network tools such as ping or domain lookups.

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?

Gives a clear usage context: 'Use to triage IPs in logs or allowlists.' It does not name an alternative sibling such as ip_cidr or state when not to use this tool, but the intended context is explicit and actionable.

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