aseprite-mcp

aseprite_pixels

Draw pixel art onto a sprite by supplying a rectangular block of pixels as hex colors or compact character strings, leaving other pixels untouched.

Instructions

Draw a rectangular block of pixels - the main tool for putting actual artwork into a sprite. The origin is the top-left of the canvas; x grows right, y grows down.

Two ways to pass data:

pixels: array of rows, each row an array of hex colours. null or "." leaves the pixel transparent.
rows + key: rows given as compact strings where each character is looked up in key. Much shorter for larger art - for example rows: ["kksskk","kssssk"] with key: {"k":"#1a1c2c","s":"#ffcd75"}.

All rows must be the same length. Drawing only touches the pixels you supply; everything else on the canvas is left alone. To keep revisions cheap, send one small block per part (outline, fill, shading) rather than repainting the whole sprite.

Tool call template

This tool declares no required parameters. Add optional parameters from the input schema as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {},
    "name": "aseprite_pixels"
  }
}

Input Schema

Name	Required	Description
`x`	No	Left edge of the block (default 0).
`y`	No	Top edge of the block (default 0).
`key`	No	Character-to-colour map, e.g. {"k":"#000000"}. "." always means transparent.
`rows`	No	Rows as character strings, resolved through `key`.
`frame`	No	Target frame (default 0).
`layer`	No	Target layer (default active layer).
`pixels`	No	Rows of hex colours, e.g. [["#000000","#ff0000"],["#ff0000",null]].
`points`	No	Alternatively, an explicit list of pixels.
`document`	No	Document to act on: a short name inside the art folder ("hero"), a relative path, or an absolute .aseprite path. Omit to use the active document.

Schema Changelog

Changes observed during successful MCP inspections.

First observedv1.0.0Sep 27, 2026

TDQS

A3.8/5.0

Behavior4/5

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

With no annotations, the description carries the full burden and does well: it declares the coordinate origin (top-left, x right, y down), states the non-destructive behavior ('only touches the pixels you supply; everything else is left alone'), and imposes the 'all rows must be the same length' constraint. What is missing is whether the edit is undoable/saved and how errors on mismatched data are surfaced.

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

Conciseness4/5

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

Content is front-loaded with the core action and coordinate convention before the two data modes. It is longer than average but nearly every sentence carries information; the numbered naming of the two approaches aids scanning.

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

Completeness4/5

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

For a 9-parameter nested tool with no annotations and no output schema, the description covers the essentials an agent needs: coordinate system, both data formats, transparency semantics, and the non-destructive guarantee. Remaining gaps (undo/save behavior, frame/layer semantics) are minor given the schema documents frame, layer, and document.

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

Parameters4/5

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

Schema coverage is 100%, so the baseline is 3. The description goes further by explaining the two data-passing modes (pixels vs rows+key), with a worked example and the meaning of '.'/null as transparent, plus the row-length constraint. These semantics exceed what the schema alone conveys.

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

Purpose4/5

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

States a concrete verb+resource ('Draw a rectangular block of pixels') and even frames it as 'the main tool for putting actual artwork into a sprite', which scopes its role. It does not, however, explicitly differentiate itself from siblings like aseprite_draw or aseprite_fill_regions.

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?

It offers strategy advice ('send one small block per part (outline, fill, shading) rather than repainting the whole sprite'), which is genuine usage guidance. But it never says when to prefer this over aseprite_draw, aseprite_fill_regions, or aseprite_text, so alternative selection is left implicit.

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

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