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

Annotations already declare readOnly, openWorld, idempotent, and non-destructive behavior. The description goes beyond by disclosing client-dependent stack selection, dual-stack behavior, DNS-based stack resolution, and that data comes from a server-side GeoIP lookup on the caller's real IP. It also warns that an unreachable 6.ip.ls means no usable IPv6.

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 main purpose is front-loaded in the first sentence, and every subsequent sentence adds relevant technical context. The description is somewhat long for a zero-parameter tool, but the stack-selection caveats are valuable and not redundant with the schema or annotations.

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 results. It names the return categories (geolocation, network info, protocol stack) and the data source, which is enough for an agent to invoke and interpret. It does not enumerate exact response fields, but for a simple zero-parameter read-only lookup this is a minor gap.

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?

There are zero parameters, so the baseline is 4. The description correctly does not invent parameter semantics, and there is nothing more to explain about inputs.

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 specific verb and resource: 'Get geolocation and network info about the caller's own public IP, plus the protocol stack.' The word 'own' clearly distinguishes it from sibling lookup tools such as ip_lookup, making the tool's scope immediately obvious.

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?

The description explicitly explains when this tool's stack choice may differ from other methods and names concrete alternatives: 'use curl -4/-6 locally to get the other stack' and 'the single-stack hostnames https://4.ip.ls / https://6.ip.ls' for clients that cannot pick a stack. This is direct, actionable usage guidance.

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