Section Line (ISO 128-40)

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

With only destructiveHint=false in annotations, the description carries the real burden and does so well: it enumerates the exact refusal conditions checked 'before any entity is written' (p1==p2, zero/parallel direction, empty label, invalid style, non-positive height), and describes how entities are distributed across GEOMETRY/CENTER/TEXT layers. That is substantive behavior beyond the annotations.

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-loaded with the action and its product, then the layer/arrow drawing detail, then refusals. Dense and largely waste-free, though the arrow-head drawing minutiae is slightly more than an agent strictly needs to select and invoke the tool.

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 9-param production tool, the definition covers what is created, where entities land, the exact payload shape, and all validation refusals. An output schema exists, so return values need not be explained, yet the description still pins down the plane contract that downstream tools depend on.

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%, so the baseline is 3, but the description adds real meaning: it explains the role-layer override semantics, that `style` is carried into the returned plane, that `direction` must not be parallel, and that `height` must be positive. This goes beyond restating schema text.

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 — 'Draw the cutting-plane line and hand back the plane a section view consumes' — with enough detail (ISO 128-40 cutting plane line) to distinguish it from line-drawing or generic entity tools. The dual output (geometry + plane payload) is stated up front.

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?

Explicitly routes the agent: `payload["plane"]` is 'feed it to the section view so the label on the plan and the label on the view cannot disagree.' This tells the agent what the tool is for in a workflow, though it never states when *not* to use it versus sibling section tools like gear_draw_section_aa.

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