cad_gltf

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

Annotations already provide idempotentHint=true and destructiveHint=false, but the description adds non-obvious behavior beyond those: export maps color attributes to PBR baseColorFactor, import creates mesh entities, and preview returns a lightweight mesh-count/bbox summary. That is useful context an agent would otherwise not know.

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 compact and front-loaded: a one-sentence summary, then three bullets for the dispatch branches, then a routing note. There is a little redundancy between the initial English sentence and the bullets, but it is minor and the structure is easy to parse.

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 tool with three discriminated action variants, an existing output schema, and annotated safety properties, the description is complete. It covers each action's semantics, highlights color and entity mapping implications, and specifies the alternative to use for non-glTF engineering formats.

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 100%, so the baseline is 3. The description adds real semantic value by explaining that the union object is dispatched by 'action' and by describing what each action does with the relevant state (current document, target or source file, mesh entities). It does not repeat field names verbatim, rather gives operational context beyond the 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?

The opening sentence states a clear verb and resource: 'Export, import or preview glTF 2.0 geometry.' The bullet list expands each action with enough detail to distinguish export, import, and preview, and the 'When not to use' note names the sibling tool (cad_file) it is not. A model can route correctly without opening the schema.

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 explicitly states the tool's intended scope (dedicated to glTF mesh assets) and contains a 'When not to use' section directing agents to cad_file for engineering formats like STEP/DXF/STL. It also specifies that the tool dispatches by action, so the appropriate usage for each branch is fairly clear.

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