Fill Selection

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

The description clearly states that the tool modifies pixel data directly on the active layer. This aligns with readOnlyHint=false, and though destructiveHint=false, the description does not claim otherwise, so there is no contradiction.

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 with three sentences, front-loading the primary action and providing essential context without unnecessary details.

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?

The description covers prerequisites, actions, and follow-up. However, it lacks details on return values, error handling (e.g., no selection), and undoability. Given no output schema, minor gaps exist.

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 description adds minimal value beyond the schema's parameter descriptions. The description does not provide additional context for opacity or blendMode beyond what is already in the schema.

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 fills the current selection with a solid color on the active layer. It uses specific verbs and resources, and differentiates from sibling tools like photopea_add_fill_layer by emphasizing the need for an active selection.

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 provides explicit guidance on prerequisites (active selection, use make_selection) and post-actions (clear_selection). It does not explicitly exclude alternatives but gives clear context for when to use this tool.

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