Add a sprite

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

No annotations are provided, so the description must carry the burden. It adds useful context like the list of built-in costumes and the tinting syntax ('ball:red'), which are not fully in the schema. However, it omits any disclosure of side effects (e.g., name conflicts, project state changes) or prerequisites beyond what is obvious. For a simple additive tool, this is adequate but not thorough.

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 two sentences with zero fluff. It front-loads the core action and costume list, then provides the tinting example, then the alternative. Every word earns its place, making it highly concise and well-structured.

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?

Despite having 9 parameters and no annotations, the description covers the primary use case (built-in costumes) and the key alternative (file-based import). Parameters like coordinates, size, and rotation are adequately documented in the schema, so the description doesn't need to repeat them. However, it doesn't mention any constraints like name uniqueness or project state, which is a minor gap for a mutation tool. Overall, it's complete for typical usage.

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 78%, so baseline is 3. The description adds meaningful detail for the 'costume' parameter by enumerating the built-in options and providing the tinting format, which goes beyond the schema's generic description. It also clarifies when to use the 'file' parameter by referencing import_character. This enhancement warrants a 4.

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 a sprite'), specifies the resource ('built-in costume'), lists the available costumes, and mentions optional tinting. It also explicitly contrasts with the sibling tool import_character for file-based art, making the purpose unambiguous and distinct.

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 provides an explicit when-not directive ('To use character art from a file, use import_character instead'), which directly guides tool selection. This is a clear alternative condition, satisfying the requirement for usage guidance.

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