rhino_surface_normal_at

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

Annotations already mark readOnlyHint=true, covering the safety profile. The description adds useful detail about the internal normalization of coordinates, but doesn't disclose return behavior, error cases, or what happens with non-surface or Brep inputs beyond the schema's phrase 'single-face Brep'.

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 concise, front-loaded sentences. The first states the operation; the second clarifies the one non-obvious input detail. No filler or redundant restatement.

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 low-complexity read-only evaluation tool with an output schema and readOnlyHint annotation, the description covers the key conceptual trap (normalized coordinates). It omits alternative-tool routing and return details, but those are largely covered by the output schema and the overall simplicity of the tool.

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 does explain u and v as domain-normalized ratios and that conversion happens internally, which adds real meaning. However, it doesn't clarify doc_id or surface_id semantics beyond the schema field names and their own descriptions.

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 opens with 'Evaluate the surface unit normal at a normalised (u, v)', which names a specific verb and resource. It does not explicitly contrast with siblings like rhino_evaluate_surface or rhino_surface_curvature_at, so it doesn't fully earn a 5.

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 gives clear input conventions: u and v are 0..1 ratios and the actual surface domain parameters are computed internally, so the LLM does not need to know domain bounds. It does not name alternatives or exclusions, but the normalized-coordinate guidance is directly actionable.

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