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

With no annotations, the description carries the full behavioral load and does it well: geodesic computation, always-positive sign, winding-order independence, and local computation with no network or quota impact. It does not mention behavior on invalid input such as fewer than 3 points, but this is a minor gap for such a simple pure function.

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?

Four compact, front-loaded sentences each earn their place: result and units, sign behavior, intended scope, and execution characteristics. There is no filler or redundancy.

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?

The tool has a single required parameter and an output schema, so the description doesn't need to explain return conventions. It supplies the key contextual facts—geodesic method, area unit, positive result, half-globe limitation, and local execution—leaving only minor edge-case behavior 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?

The schema already documents `points` and the `lat`/`lon` fields completely, so the baseline 3 applies. The description adds useful context like 'ring' and the 3+ requirement, but it doesn't elaborate on ordering, precision, or repeated closing coordinates—details that would be extra value beyond the schema.

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 operation—computing enclosed area in square metres from a geodesic ring of 3+ coordinates—making it instantly distinguishable from line-measurement siblings like geo_distance and geo_length. The '3+ coordinates' condition further defines the expected input resource.

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?

It gives clear intended use ('zones and boundaries') and an explicit exclusion ('not for polygons covering more than half the globe'). It stops short of naming alternative tools for that exclusion, but the guidance is sufficient for an agent to understand when this tool applies.

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