pixel_draw_rect

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

The description adds behavioral details beyond annotations: it specifies the return JSON structure, optional preview rendering, and the erasure effect of 'transparent'. It does not contradict the readOnlyHint=false, destructiveHint=true, idempotentHint=true 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?

The description is concise (5 lines), front-loaded with the core action, and includes essential details like return format and error handling. Every sentence serves a purpose.

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?

Given the simple nature of the tool, the description covers behavioral expectations, coordinate system, special color handling, output format, and error behavior. It is sufficient for an agent to use correctly.

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?

The description clarifies coordinate semantics (top-left, pixels) and the effect of color='transparent'. The schema individually describes each parameter, but the description adds overarching context that the schema lacks.

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 clearly states it draws a filled or outlined rectangle on a canvas, specifying behavior for coordinates and size. It distinguishes itself from sibling tools like pixel_draw_line or pixel_draw_ellipse by being rectangle-specific.

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 explains coordinate conventions (top-left), pixel units, and the special 'transparent' erasure behavior. It does not explicitly list when not to use this tool or mention alternatives, but the context is clear enough for typical use cases.

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