lentera-aseprite-mcp

set_cel_opacity

Adjust the opacity of a specific cel (layer and frame) in Aseprite, enabling precise control over pixel art transparency.

Instructions

Set the opacity of a specific cel (layer+frame combination).

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "opacity": "<opacity>"
    },
    "name": "set_cel_opacity"
  }
}

Input Schema

Name	Required	Description
`frame`	No
`layer`	No
`opacity`	Yes	Opacity 0-255

Schema Changelog

Changes observed during successful MCP inspections.

First observedv1.0.0Aug 14, 2026

TDQS

B3.1/5.0

Behavior2/5

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

No annotations are provided, so the description carries the full burden of behavior disclosure. As a mutation tool, it should mention whether opacity is applied to the active cel when layer/frame are omitted, whether the change is reversible, or any prerequisites (e.g., open sprite). The single-sentence description offers none of this.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness3/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is a single, waste-free sentence, but it is too brief to cover the necessary behavioral and parameter details for a tool with three parameters and no annotations. The conciseness is good, but the overall structure under-specifies.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness2/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

The tool has a simple schema but no output schema or annotations, and the description does not explain default behaviors, success/failure conditions, or how layer and frame are used when omitted. Given the complexity of cel addressing, the description is incomplete.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters2/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The schema only describes the opacity parameter (0-255), leaving frame and layer with no schema descriptions. The description adds the conceptual meaning that a cel is a layer+frame combination, which helps interpret frame and layer. However, it does not clarify whether these are optional (since only opacity is required), what they default to, or whether they expect names or indices.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the verb 'set', the resource 'opacity', and the scope 'a specific cel (layer+frame combination)'. This distinguishes it from sibling tools like set_layer_properties, which operate at the layer level, and clear_cel, which removes a cel.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The phrase 'specific cel' implies this is for per-cel opacity adjustments, which is distinct from layer-wide properties. However, it does not explicitly state when to use this tool or when to prefer set_layer_properties, nor does it mention alternatives or exclusions.

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