measure

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

Annotations already declare readOnlyHint and idempotentHint, so safety is covered. The description adds valuable behavioral details beyond annotations: it specifies the output (dx/dy, centre distance, compass direction, edge-to-edge gap) and the input formats, which enriches the agent's understanding of what the tool does and returns.

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 two sentences with no filler. It front-loads the purpose and then details input formats and outputs. Every sentence earns its place, making it concise and well-structured.

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 read-only measurement tool with an output schema present, the description covers inputs and outputs well. The only gap is the unexplained 'path' parameter, but since the tool is simple and read-only, the description is largely complete. The output schema handles return value details, so the description does not need to repeat them.

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 schema provides no descriptions (0% coverage), so the description must compensate. It explains the semantics of parameters 'a' and 'b' (footprint ref, pad, or point in mm) but leaves 'path' completely unexplained. This partial coverage earns a 3, as it helps but does not fully clarify all parameters.

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 clearly states the tool measures distance between two items, with a specific verb and resource. It also explains the accepted input formats (footprint refs, pads, points) and lists the returned values, making it distinct from siblings like search or list_components, which serve different purposes.

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 description implies usage (when you need distance between two items) but does not explicitly state when to use it versus alternatives or mention any exclusions. Since no sibling tool measures distances, the context is clear, but explicit guidance is absent.

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