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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is well covered. The description adds the output fields (country, region, city, ISP, timezone), which provides some behavioral context about the return data. However, it does not disclose other traits like rate limits or error behavior, but the low complexity and existing annotations make this adequate.

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 a single, front-loaded sentence that lists the core output fields without any fluff or redundant explanations. Every word earns its place, making it highly efficient.

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 simple read-only lookup with one optional parameter, an output schema, and clear annotations, the description is sufficient. It covers the purpose and key return values. The only gap is the lack of explicit usage context, but the simplicity of the tool makes this a minor omission.

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 schema description coverage is 100%, with the 'ip' parameter clearly documented as 'IPv4/IPv6; omit for caller IP'. The description adds no additional parameter semantics beyond what the schema already provides. Baseline 3 is appropriate given full schema coverage.

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 clearly states the resource (IP address) and the function (geolocation and ISP), listing specific fields like country, region, city, and timezone. While it lacks an explicit verb, the name 'ip_lookup' and title 'IP geolocation' make the action clear. It distinguishes itself from sibling tools by focusing on IP-specific data.

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 provides no explicit guidance on when to use this tool versus alternatives, nor does it mention exclusions or prerequisites. The only usage hint ('omit for caller IP') appears in the schema, not the description. The purpose is implied but not directly stated as a use case.

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