Artist's selection

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

Beyond the readOnlyHint annotation, the description discloses the empty case ({empty:true}) and the exact behavior of the mask parameter (rows with '#'). This adds meaningful behavioral detail about output format and option effects.

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?

Three sentences, each earning its place. The primary purpose is front-loaded, the mask explanation is concise, and there is no redundant or filler content.

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 single-parameter read-only tool with no output schema, the description covers the main use case, the empty state, the mask behavior, and its relationship to other tools. Nothing essential for correct invocation is missing.

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 explain the mask parameter, and it does clearly: mask=true adds the exact shape as rows when not a plain rectangle. It also implies the default return is a rect, giving context for the parameter's effect.

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 the tool returns the artist's selected region in Aseprite, explains its purpose for resolving references like 'this part', and distinguishes it from siblings by focusing on selection. The verb and resource are specific and non-tautological.

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?

It explains when to use the tool (to get the selection for requests needing coordinates) and hints that most tools accept a rect directly, implying you may not need this if you already have coordinates. However, it does not explicitly name alternatives or state exclusions, so it stops short of full guidance.

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