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

With no annotations, the description carries the full burden of behavioral disclosure, but it only restates the calculation. It does not say whether the midpoint is a geodesic/true great-circle midpoint or a simple average of coordinates, what coordinate format is expected, or what the return value looks like.

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 one front-loaded sentence with no filler. The parenthetical definition is helpful, and every phrase earns its place.

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 calculation tool this is borderline sufficient, but with no annotations and no output schema, the description should state the expected return format and how inputs are passed given the empty schema. It tells what to compute but not the exact calling contract.

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 description names lat1/lon1 and lat2/lon2, which adds meaning over the empty input schema, but it doesn't define units, requiredness, formatting, or ordering. The mismatch with the schema, which declares zero properties, makes the invocation contract ambiguous.

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 clear verb and resource: calculate the midpoint/halfway point between two GPS coordinates, and names the four inputs. It is distinct from geometry tools like x402-midrange or x402-midhinge, though it doesn't explicitly disambiguate from coordinate siblings like x402-geo-distance or x402-bearing.

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?

There is no guidance on when to use this tool versus alternatives, and no exclusions or alternative tool mentions. The only implicit usage context is that it applies to GPS coordinate pairs, but an agent cannot tell when to prefer this over related geo tools.

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