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

Annotations already declare readOnly, idempotent, non-destructive and openWorld=false, so safety is covered. The description adds genuinely new behavioral context: a per-call price of $0.003 USDC via x402 on eip155:8453, which the agent cannot learn from structured fields. It stops short of saying what happens on malformed input.

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?

Two sentences, front-loaded with the core action, and the returned fields are grouped efficiently. Minor redundancy: the category list appears in the title and again in the second sentence, costing a few tokens without new information.

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 correctly enumerates return values (canonical/expanded forms, integer and hex, version, scope, routability, reverse DNS), and pricing is disclosed. The only real gap is behavior on invalid or non-address input.

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?

One parameter at 0% schema description coverage, so the description must carry the load. It does identify the parameter's meaning ('an IPv4/IPv6 address') and hints at accepted families, but says nothing about whether CIDR notation, ports, or bracketed IPv6 forms are accepted.

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 pair ('parse and classify') plus an explicit resource ('an IPv4/IPv6 address'), followed by an enumeration of the classification outputs. An agent can immediately tell this operates on a single address, unlike cidr_info or ip_range_to_cidr which work on blocks.

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?

Usage is only implied: you have an IP string and want it classified. No explicit when-to-use statement and no named alternatives, even though cidr_info, ip_range_to_cidr, and dns_reverse are adjacent siblings an agent could confuse it with.

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