silhouette_add_polyline

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

Annotations already declare this is a non-readonly, non-destructive, non-idempotent, closed-world mutation, so the safety profile is covered. The description adds genuinely useful behavior beyond that: coordinates are in millimeters with Y pointing down, plus minimum point counts per mode. It stops short of saying what happens on degenerate input or what the call returns.

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 compact sentences with the core action and coordinate convention front-loaded and the mode rules trailing. No filler, though the parenthetical unit note could be folded in more cleanly.

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 five-parameter creation tool with no output schema and zero schema coverage, the definition covers geometry and mode but omits which design is targeted, what layer values mean, and any error behavior. Adequate to call correctly with defaults, not fully complete.

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 0%, so the description must carry parameter meaning. It does well for the two most consequential parameters — points (mm units, Y-down, [x,y] pairs) and closed (shape semantics and minimum counts) — but leaves the required design parameter and the layer/label fields entirely unexplained.

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 and resource — 'Add a custom path through the given [x, y] points' — and the closed/open distinction separates it in spirit from sibling primitives like add_polygon and add_line. It does not explicitly name a sibling to route against, which keeps it at 4.

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?

Usage is only implied through the point-count rules (closed needs >= 3, open needs >= 2), which effectively tell the agent when each mode is valid. There is no explicit guidance on when to choose this tool over add_polygon, add_line, or add_rectangle.

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