measure

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

With no annotations, the description carries the full burden and does so thoroughly: it discloses units, coordinate frames, override semantics ('mass_g overrides purchased parts'), and output caveats ('facts only', 'no winner'). This gives an agent an accurate model of behavior beyond the bare tool name.

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 dense and every clause adds information, with the core purpose front-loaded before the mode catalogue. It is concise for the amount of behavior covered, though a single wall of text with no line breaks or bullets makes it harder to scan than it could be.

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 21-parameter tool with no annotations and no schema descriptions, this is a strong effort: it covers units, modes, source mesh, and response formats. It is not fully complete because the model-source parameters (scad_file, scad_content, variables, include_paths) are never explained, which an agent would need to invoke the tool correctly.

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?

Schema description coverage is 0%, so the description must compensate; it explains the meaning of most parameters (parts, mode, section_axis/offset, about_axis, points, rays, polyline, quality, response_format). However, several schema parameters are left unexplained, including scad_file, scad_content, variables, include_paths, and orientation, so the compensation is not complete.

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 opening line 'Exact numbers from a model's geometry (mm)' states the tool's function with a specific resource and unit, and the mode list (model, parts, section, mass, probe, etc.) defines its scope precisely. This clearly separates measurement from visual or export tools like render or export_model.

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?

'Prefer this over judging a picture' explicitly tells an agent when to choose this tool, and the mode descriptions give direct selection criteria (e.g., use 'mass' for grams, 'section' for cut contours). It does not name sibling alternatives or state exclusions, but the contextual guidance is strong.

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