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

No annotations are provided, so the description carries the full behavioral burden. It conveys a pure read-only calculation ('Calculate') with a constrained output range (0-360 degrees), which adequately signals safety. It does not disclose edge-case behavior (antipodal points, invalid lat/lon values), numeric precision, or the return format beyond the degree range, which an agent would need to consume the result correctly.

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?

One ~25-word sentence that front-loads the operation and packs in inputs and output range with no filler. The leading 'Bearing:' prefix redundantly restates the tool name, a minor structural blemish that keeps this from a 5.

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 low-complexity calculation the core semantics are covered, but the input schema declares zero parameters while the description requires four, and no output schema exists. An agent following the schema would find no slot to supply coordinates, while a description-following agent must guess exact parameter names and formats — a real invocation risk the description fails to resolve.

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?

With an empty schema, the description must supply the input contract, and it does name the four inputs (lat1/lon1 and lat2/lon2), earning credit above the 0-param baseline. It stops short of specifying types, ranges, or how the values should be passed (four scalars vs. two coordinate objects), and the empty schema weakens confidence in the described contract.

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 (initial bearing between two GPS coordinates), and pinpoints the output as compass direction in degrees 0-360. Naming lat1/lon1 and lat2/lon2 makes the contract unambiguous, and this is clearly distinct from sibling tools like x402-geo-distance or x402-compass-direction.

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 intended scenario, needing the initial bearing between two GPS points, is implied directly by the purpose statement, so an agent can infer when it applies. However, there is no explicit guidance about when not to use it or which alternative to prefer (e.g., x402-geo-distance, x402-midpoint, x402-compass-direction), and no prerequisities or exclusions are stated.

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