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

No annotations are provided, so the description carries the full burden. It does disclose a meaningful behavioral trait — that the result is the 'initial' (not final) great-circle bearing — which matters for long distances. However it says nothing about units, north reference, range, auth, or behavior for identical points.

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 front-loaded sentence with zero filler. The operative verb and the two required inputs are all conveyed immediately, and no sentence fails to earn 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?

An output schema exists, so return values need not be described. For a pure-computation tool with no annotations and nested object parameters, the definition covers the core purpose but omits edge cases (identical points, antimeridian crossing) and the initial-vs-final distinction beyond a single adjective.

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?

Reported schema coverage is 0% at the top level, and the description adds no information about 'from' and 'to'. The nested lat/lng schemas are, however, unusually thorough on accepted coordinate formats, and the names from/to are self-explanatory, so the semantic gap is limited.

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 and resource with a qualifier: 'Calculate the initial true bearing between two GPS coordinates.' This is clearly distinguishable from calculate_distance and calculate_cross_track_error, though it does not name those siblings explicitly. An agent can identify the operation and its inputs without opening the schema.

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 guidance on when to use this versus calculate_distance or calculate_cross_track_error, which are the obvious overlapping siblings in a coordinate-math suite. There are no stated prerequisites or exclusions.

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