Add a costume to a sprite

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

With no annotations provided, the description carries the full burden of behavioral disclosure, but it only restates the action and the two input sources. It does not mention any side effects, permissions, error handling, or return behavior. The description is essentially a rephrasing of the title with no added behavioral depth.

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 concise sentence that front-loads the core action and quickly clarifies the two input sources. Every word contributes; 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?

The tool has four parameters and no output schema, but the operation is simple. The description, combined with the schema, conveys the essential inputs. However, it does not address potential edge cases like what happens if the sprite doesn't exist, whether costumes are appended or replaced, or any file path constraints. These gaps are minor for a straightforward add operation but prevent a higher score.

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 already provides descriptions for all four parameters (file, name, target, costume) with clear meanings, so the description does not need to add much. The description's mention of 'built-in shape or an image file' maps to the costume and file parameters, but it adds no new semantics beyond what the schema covers. Baseline of 3 is appropriate given 100% schema coverage.

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 action (adds another costume) and the target (existing sprite), and specifies two sources: built-in shape or image file. This distinguishes it from siblings like add_sprite or add_backdrop by focusing on costumes and the existing-sprite constraint.

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 implies usage by stating 'existing sprite', which suggests the tool is not for creating sprites, but it does not explicitly mention alternatives or when not to use it. There is no guidance on when to prefer this over add_backdrop or add_sprite, though the existing-sprite wording offers some context.

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