select_ellipse

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

With no annotations, the description must carry the behavioral burden. It explicitly states that the selection is 'replaced', disclosing the side effect that the previous selection is lost. However, it does not explain coordinate interpretation (e.g., whether x,y is the center or top-left), units, or any operational specifics. The negative side effect is clear, but behavioral details remain minimal.

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 a single, focused sentence with no filler or redundancy. It front-loads the core action and is appropriately sized for a simple selection tool, making it highly efficient.

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 tool has five required parameters, zero percent schema description coverage, and no annotations. The presence of an output schema reduces the need to explain return values, but the description is far too sparse to provide the necessary context for parameter handling, coordinate system, and expected behavior. It leaves significant gaps for an AI agent.

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 schema has five required parameters with zero textual description coverage. The tool description does not explain the roles of x, y, width, height, or image_id, and notably x and y are ambiguous (center vs top-left) without additional context. This is a critical omission for an AI agent to invoke the tool correctly.

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 uses a specific verb 'Replace' and a specific resource 'the selection', clearly indicating that the tool replaces the current selection with an ellipse. This distinguishes it from sibling tools such as select_rectangle, select_none, and invert_selection, so the purpose is unambiguous.

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 phrase 'Replace the selection with an ellipse' provides clear context: it is used when you want to set the selection to an elliptical shape. It does not explicitly mention alternatives or exclusions, but the usage is effectively self-evident, so it earns a 4 rather than a 5.

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