rhino_document_units_set

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

Annotations declare readOnlyHint=false, which is consistent with the 'Set' semantics; there is no contradiction. The description adds the key behavioral nuance that existing geometry may optionally be scaled, which is useful context beyond the annotation. However, it does not disclose the default behavior when scale_existing is omitted (raw coordinates reinterpreted) or any side effects on the active document.

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?

A single 11-word sentence that front-loads the verb and resource and includes the one important behavioral caveat. Every word earns its place with zero 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?

For a simple setter with an output schema and richly documented parameters, the description captures the core operation and the key behavioral nuance (optional scaling). The main missing element is routing guidance relative to rhino_set_units, which is an ambiguity gap rather than a functional one.

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?

Even though the context signal reports 0% schema description coverage (likely a top-level-only computation), the nested $_UnitsSetIn schema provides thorough descriptions for all three parameters: accepted unit aliases, doc_id targeting, and the exact scale_existing semantics. The tool description itself adds nothing beyond echoing 'scaling existing geometry,' so the schema carries the load and a baseline of 3 is appropriate.

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 states a specific verb ('Set'), a clear resource ('the document unit system'), and adds the optional scaling behavior that defines this tool's scope. It does not, however, distinguish itself from the near-identically-named sibling rhino_set_units, so an agent cannot tell which of the two to pick without opening both schemas.

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 no guidance on when to use this tool versus alternatives like rhino_set_units or the read-oriented rhino_document_units_get. No conditions, exclusions, or alternative routing are provided, so the agent must guess which tool fits a given intent.

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