Measure a distance

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

Beyond the readOnlyHint annotation, the description discloses important behavioral context: units are 'm' only when a metric anchor exists, otherwise 'relative', and the agent must always report units and scale_source and never call relative units metres. This is substantive operational guidance.

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 three sentences with no filler: operation, unit behavior, and reporting instruction. Critical information is front-loaded and every sentence 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 measurement tool it covers the main hazards around metric vs relative units and reporting requirements. However, with no output schema, scale_source is left undefined and the response shape is not described, so an agent still has some ambiguity about the full return value.

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 0% schema description coverage, the description needs to compensate for parameter meaning. It adds the key clarification that point_a and point_b are world-frame points, but it does not explain scan_id, coordinate ordering, or how points relate to the scan. The compensation is partial.

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 — measuring distance between two WORLD-frame points — and names the endpoint (POST /measure). This clearly differentiates it from the sibling scene_measure_angle by the core concept of distance.

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 phrase 'Distance between two WORLD-frame points' implies the main use case, but the description never explicitly says when to prefer this tool over alternatives like scene_measure_angle, nor does it provide when-not-to-use conditions. Usage is inferred rather than stated.

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