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

Annotations already declare readOnlyHint=false, openWorldHint=false, and destructiveHint=true, so the write/irreversible profile is covered. The description adds genuinely useful behavior: creating a part class also spawns a default style and a default part. It omits permissions, whether the default objects are named/identifiable afterward, and how the referenced-class parameters (parent, mirror, require, renderWith) must resolve.

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?

Two short sentences, front-loaded with the action and immediately followed by the side effect. No filler, though the brevity leaves the parameter semantics unresolved rather than being an over-length problem.

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 an 11-parameter mutation tool with 9% schema coverage and no output schema, the description is thin: it says nothing about required relationships between the self-referential class IDs, position semantics, or what the tool returns (e.g., the new class id). Only the default style/part side effect is disclosed.

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 only 9% — just hasVariants is documented — so the description carries the burden and adds almost nothing. It does not explain the semantics of renderPosition vs uiPosition, rotatePointX/Y, or the four self-referential *PartClassId fields (parentPartClassId, canMirrorPartClassId, canRequirePartClassId, renderWithPartClassId), which are the hardest to guess.

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 ("Create a part class") and situates it inside a template, which distinguishes it from create_template and create_part. It does not explicitly contrast with create_part or create_style, which are the closest siblings and could be confused with the default style/part side effect.

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 create_part or update_part_class, and no prerequisites stated beyond the implicit requirement that a template exist. The agent must infer that templateId must reference a pre-existing template.

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