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

Annotations already declare readOnly, idempotent, and openWorld, so the safety profile is covered. The description adds genuinely useful context beyond them: geodata comes from a local GeoLite2 database (implying possible staleness/accuracy limits) and domain_ip returns only the first IPv4 address, not all records. It stops short of describing failure behavior for malformed IPs or unresolvable domains.

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 opens with the resource ('Network facts:') and then walks the four modes in the same order as the enum, so the reader maps description to schema effortlessly. The closing 'No API key, no account and no sign up' is short and earns its place as a setup constraint.

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 carries the burden of explaining return values, and it does so for every mode (IP, user-agent string, country/city/coords/timezone, resolved address). For a trivial two-parameter lookup this is nearly complete; only error/empty-result behavior for invalid input is unstated.

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%, so the baseline is 3; the description earns an extra point by clarifying the conditional requirement that value applies only to the last two kinds, which the schema's flat 'required: kind' does not make explicit. It does not add format constraints (e.g. whether CIDR or hostnames with trailing dots are acceptable) beyond the schema's maxLength.

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?

Names a specific resource (network facts) and enumerates the four concrete outputs it can produce: client_ip, user_agent, GeoIP details for reverse_ip, and A-record resolution for domain_ip. An agent can tell exactly which mode answers which question without consulting the schema.

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?

Each kind is tied to a clear use condition ('describe this request' vs 'looks up the IPv4 address in value' vs 'resolves the domain in value'), which effectively tells the agent when to pick each mode. It also states the prerequisite that no API key, account, or sign-up is needed. It does not name any alternative sibling tool, but none of the listed siblings overlaps this function.

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