Add a backdrop to the stage

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

With no annotations provided, the description carries the behavioral burden. It transparently discloses the key side effect: 'The newly added backdrop becomes the one shown.' It does not detail edge cases like list ordering or failure behavior, but it covers the important visible outcome.

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?

Two concise sentences with the action, options, and side effect front-loaded. Every sentence adds useful information with no filler.

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 3-optional-param tool with no output schema, the description covers what can be added, where it applies, and what happens when added. It could mention naming behavior for file imports, but the schema's 'name' description already covers that.

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 description coverage is 100%, so the baseline is 3. The description adds some value by enumerating built-in names and implying file-vs-built-in exclusivity, but it does not explain parameter combinations or conflicts in depth.

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?

States a clear verb and resource: 'Adds a stage backdrop,' with explicit sub-cases (built-in or file). It also distinguishes this from sibling tools like add_costume or add_sprite by anchoring to the stage and the visible result.

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 gives clear context: use this to add a stage backdrop, either built-in or from a file. It does not explicitly name alternative tools or exclusions, but the stage-backdrop framing makes the intended use obvious.

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