Set the opacity of a specific cel (layer frame) in an Aseprite file to adjust transparency. Provide the filename, layer name, frame index, and opacity value from 0 to 255.
Set one cel opacity from 0 to 255.
| Name | Required | Description | Default |
|---|---|---|---|
| opacity | Yes | ||
| filename | Yes | ||
| layer_name | Yes | ||
| frame_index | Yes |
Changes observed during successful MCP inspections.
v1.0.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description carries the full burden of behavioral disclosure. 'Set' implies mutation, but the description does not explain persistence, idempotency, validation failures, or whether the operation modifies the current document state in any noteworthy way. The 0–255 range merely duplicates what the input schema already states.
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 short sentence with no filler or wasted words. The action is front-loaded and the only stated constraint is the opacity range, which is immediately relevant to callers.
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 4-parameter mutation tool with no annotations and no output schema, this description is too thin. It omits parameter meanings, alternative routing, and behavioral caveats, leaving an agent to infer how the cel is located and what happens when the operation is applied.
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 0%, so the description needed to compensate for all four parameters. It only addresses the opacity range, which is already encoded in the schema, and provides no meaning for filename, layer_name, or frame_index, nor how they jointly identify the target cel.
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 an explicit verb 'Set' and a specific resource 'one cel opacity', with a numeric range. This distinguishes it from siblings like set_layer_opacity (targets a layer, not a cel) and tween_cel_opacity_eased (animates opacity over time rather than setting a single value).
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?
There is no guidance on when to use this tool rather than an alternative. It does not mention that set_layer_opacity would affect an entire layer, that tween_cel_opacity_eased would animate opacity across frames, or any prerequisites for targeting a valid cel.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.