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

Adds real behaviour beyond the readOnly/destructive/openWorld annotations: it enumerates the exact expression grammar evaluated ('arithmetic, comparisons, min/max/round, a if c else b; nothing else is evaluated'), states the output is in mm, and explains that placement happens later via `familles`/`instances` in a CAO scene. Annotations confirm safety; the description supplies the evaluation semantics they cannot.

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?

Front-loads the WHEN condition and keeps every clause informative, but the run-on second sentence packs the expression grammar, return payload, and placement instructions together and could be broken up for scanability.

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 correctly describes the return payload (computed values, constraint findings, solids in mm) and explains how the result reaches a scene as boxes/IFC objects. For a two-param, nested-object tool with annotations covering safety, little is missing beyond an explicit sibling reference.

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 coverage is 100% and both parameters are fully documented in the schema, so the baseline is 3. The description restates the family structure (parameters, formulas, constraints, solids) without adding syntax or format detail the schema lacks, so it neither helps nor hurts.

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: 'try a family DEFINED AS DATA, like a Revit family', with the scope (typed/bounded params, formulas, constraints, solids) made explicit. It implicitly carves itself out from catalogue-based siblings by saying 'no catalogue has', but never names cao_familles or cao_bibliotheque_familles, so an agent must infer the split.

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 'WHEN a custom parametric object is needed that no catalogue has' clause gives a clear triggering condition with concrete examples (shelf, counter, pergola, technical box). It does not name the catalogue sibling it is meant to be used instead of, nor state when NOT to use it, so routing is implied rather than explicit.

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