Read a rectangular RGBA pixel region from an Aseprite cel as JSON, specifying filename, coordinates, width, height, layer, and frame. Retrieve precise pixel data for scripts and asset pipelines.
Read a rectangular RGBA region from a cel as JSON.
| Name | Required | Description | Default |
|---|---|---|---|
| x | Yes | ||
| y | Yes | ||
| width | Yes | ||
| height | Yes | ||
| filename | Yes | ||
| layer_name | No | ||
| frame_index | No |
Changes observed during successful MCP inspections.
v1.0.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the behavioral disclosure burden. It does disclose that the operation is read-only and that the result is JSON-encoded RGBA data. However, it omits useful behavioral context such as coordinate-space semantics, bounds/out-of-range behavior, the meaning of layer_name and frame_index defaults, and whether regions are clipped or error when outside the cel.
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?
One short, front-loaded sentence that conveys the operation, resource, data format, and output type. There is no padding, repetition, or unnecessary detail.
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 7 parameters, 0% schema description coverage, no annotations, and no output schema. The description is too sparse for an agent to confidently call it correctly: it doesn't clarify the cel coordinate system, how layer_name and frame_index select the cel, or what the JSON structure looks like. More context is needed for reliable invocation.
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 must compensate by explaining parameters. It provides minimal inference for width/height/region and 'from a cel', but it does not explain x/y coordinates, layer_name, frame_index, or how the rectangle maps to cel coordinates. The schema's raw integer bounds offer no semantic meaning.
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 specific verb ('Read'), a specific resource ('a rectangular RGBA region from a cel'), and the output format ('as JSON'). It clearly distinguishes itself from composite/read tools like get_composite_rect by anchoring the operation to a cel, while still being immediately understandable.
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?
No guidance is provided about when to use this tool versus alternatives such as get_pixel_color, get_composite_rect, or get_sprite_info. The term 'from a cel' weakly implies it reads raw cel pixels rather than composite pixels, but no explicit when-to-use or when-not-to-use guidance is present.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.