list_faces

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

With no annotations, the description carries the burden and does well: it discloses extra fields for cylindrical faces, the axis/radius/point-on-axis semantics for holes, the frame a component is listed in, and the critical caveat that a part's indices shift as features are added while a component's are stable. It omits nothing safety-relevant for what is a read-only listing, though it doesn't discuss error or empty-result behavior.

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?

Purpose is front-loaded in the first sentence and each subsequent sentence adds distinct value (cylindrical faces, component frames, index stability, add_mate reference). It is dense and somewhat parenthetical, but no sentence is filler.

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?

With no output schema, the description must describe return values, and it does — listing the face fields and the extra cylindrical-face fields. Combined with the component-frame and index-stability notes, it is complete enough to call the tool correctly, though edge cases (no part open, unknown component) are unaddressed.

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 single 'component' parameter has 0% schema coverage, so the description must compensate — and it does, explaining that it selects a component of the current assembly listed in its own frame, and that for a sub-assembly it returns every part's faces in the sub-assembly's frame each naming its part. This adds substantial meaning beyond the bare anyOf string schema.

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 ('List the part's faces') and enumerates exactly what is returned (index, planar?, normal, area, centre). This clearly distinguishes it from siblings like list_edges, list_bodies and list_components.

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?

Usage is implied ('for inspection', and that add_mate consumes the indices as '#5'), so the agent can infer the downstream purpose. However, there is no explicit when-to-use/when-not versus list_edges or guidance on when to pass the component argument, so guidance remains implicit rather than stated.

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