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

No annotations are provided, so the description carries the burden, but this is a pure stateless calculation with no side effects, so risk is low. It clarifies the semantic of 'midpoint' as the 'halfway point', which is useful, yet says nothing about coordinate format expectations, invalid input handling, or antipodal edge cases.

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 well-formed sentence with the action front-loaded. The 'Midpoint:' prefix mildly restates the tool name, but nothing else is wasted.

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?

Four parameters with 0% required and no output schema; the description explains the computation but not the return shape (e.g., a lat/lon object) or the expected coordinate representation, which an agent must know to use the result. Adequate for a simple calculator but with clear gaps.

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 description coverage is 100%, so the baseline is 3 even though the schema text itself is poor ('Lat1 to process'). The description adds meaning by framing the four params as ordered lat/lon pairs of two GPS coordinates, which is marginally more than the schema conveys.

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?

States a specific verb ('Calculate') and resource ('midpoint between two GPS coordinates') with the input shape (lat1/lon1, lat2/lon2). The purpose is unambiguous and distinguishable from geographic siblings like distance or bearing, though it never names an alternative to contrast with.

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?

No indication of when to choose this tool over the dozens of geographic/math siblings (x402-distance, x402-lerp, x402-geo-distance, x402-interpolate). The description states only what it computes, leaving selection entirely to inference.

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