pcb_create_fill

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

Annotations already declare this is a non-read-only, non-idempotent, non-destructive write, so the safety profile is covered. The description adds the coordinate frame and units, but says nothing about whether the fill can be undone, whether a net association is required, or what happens on overlap with existing copper.

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?

The purpose is front-loaded in the first clause, followed by coordinate semantics and cross-references. The sentence about lengths ('widths, diameters') is generic boilerplate that does not apply to a polygon fill, a small amount of wasted text.

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?

There is no output schema, so the description carries the burden of explaining results and side effects, which it does not. Coordinate semantics are well covered, but for a geometry-creating mutation it omits return value, undo/reversibility, and interaction with existing fills.

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 baseline is 3, but the description adds genuinely new meaning the schema lacks: coordinates are in mil (0.001 inch), relative to canvas origin, +X rightward and +Y upward. That unit/frame clarification is directly needed to supply a correct polygon.

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 ('Create a fill region on the PCB'), which is clear on its own. However, it never distinguishes the tool from close siblings like pcb_create_pour or pcb_create_region, so an agent must guess which of the three creation tools to pick.

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 routes the agent to pcb_canvas_origin and pcb_convert_coordinates for the coordinate system, which is useful operational guidance. It gives no when/when-not advice relative to pcb_create_pour or pcb_create_region, so selection between the geometry-creation siblings is left to inference.

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