aseprite-ai-artist

Overview Schema Source Related Servers Discussions Admin

Cels

cel

Destructive

Manage one layer's image per animation frame in Aseprite: create, move, link, tween, or oscillate artwork to animate limbs and static parts without redrawing.

Instructions

Manage cels — one layer's image on one frame. Ops: 'list', 'create', 'clear', 'delete', 'move', 'copy', 'link', 'unlink', 'set' (position/opacity), 'tween', 'oscillate'. 'move' is how you shift a whole limb between frames without redrawing it; 'link' shares one image across frames so a static part of a cycle stays in sync. 'tween' interpolates position or opacity between two frames with an easing curve; 'oscillate' adds a sinusoidal position offset over a frame range — both fill in any missing in-between cels from the start cel, in one transaction.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`x`	No	Cel origin, for 'set' and 'move'.
`y`	No
`dx`	No	Relative move.
`dy`	No
`op`	Yes
`to`	No	For 'tween': end value — {x,y} for property 'position', 0-255 for 'opacity'.
`frame`	No	1-based frame number. Omit to use the active frame.
`layer`	No	Layer name. Omit to use the active layer.
`phase`	No	For 'oscillate': 0-1 fraction of one period.
`easing`	No	For 'tween'.	linear
`frames`	No	For 'link' across a range.
`period`	No	For 'oscillate', in frames. Default: the whole fromFrame..toFrame span.
`sprite`	No	Which sprite: its id as '#7' (what every result reports back, and the only unambiguous form — two unsaved documents are both called 'Sprite'), its filename, or its display name. Omit to use the sprite Aseprite has focused.
`opacity`	No
`toFrame`	No
`toLayer`	No
`property`	No	For 'tween'.
`fromFrame`	No	For 'tween'/'oscillate': the start frame.
`amplitudeX`	No	For 'oscillate'.
`amplitudeY`	No	For 'oscillate'.

Output Schema

TableJSON Schema

Name	Required	Description
`cels`	No
`frames`	No	Only present for 'tween' and 'oscillate': one entry per frame touched, ascending.
`sprite`	Yes
`applied`	No

Schema Changelog

Changes observed during successful MCP inspections.

Changed10 schema fields changedv0.4.0Sep 30, 2026

addedInput schema / properties / amplitudeX

Added value: +{
+  "default": 0,
+  "description": "For 'oscillate'.",
+  "type": "integer"
+}

addedInput schema / properties / amplitudeY

Added value: +{
+  "default": 0,
+  "description": "For 'oscillate'.",
+  "type": "integer"
+}

addedInput schema / properties / easing

Added value: +{
+  "default": "linear",
+  "description": "For 'tween'.",
+  "enum": [
+    "linear",
+    "ease_in",
+    "ease_out",
+    "ease_in_out",
+    "smoothstep"
+  ],
+  "type": "string"
+}

addedInput schema / properties / fromFrame

Added value: +{
+  "description": "For 'tween'/'oscillate': the start frame.",
+  "exclusiveMinimum": 0,
+  "type": "integer"
+}

changedInput schema / properties / op / enum

Previous value: -[
-  "list",
-  "create",
-  "clear",
-  "delete",
-  "move",
-  "copy",
-  "link",
-  "unlink",
-  "set"
-]New value: +[
+  "list",
+  "create",
+  "clear",
+  "delete",
+  "move",
+  "copy",
+  "link",
+  "unlink",
+  "set",
+  "tween",
+  "oscillate"
+]

addedInput schema / properties / period

Added value: +{
+  "description": "For 'oscillate', in frames. Default: the whole fromFrame..toFrame span.",
+  "minimum": 2,
+  "type": "integer"
+}

addedInput schema / properties / phase

Added value: +{
+  "default": 0,
+  "description": "For 'oscillate': 0-1 fraction of one period.",
+  "maximum": 1,
+  "minimum": 0,
+  "type": "number"
+}

addedInput schema / properties / property

Added value: +{
+  "description": "For 'tween'.",
+  "enum": [
+    "position",
+    "opacity"
+  ],
+  "type": "string"
+}

addedInput schema / properties / to

Added value: +{
+  "anyOf": [
+    {
+      "additionalProperties": false,
+      "properties": {
+        "x": {
+          "type": "integer"
+        },
+        "y": {
+          "type": "integer"
+        }
+      },
+      "required": [
+        "x",
+        "y"
+      ],
+      "type": "object"
+    },
+    {
+      "maximum": 255,
+      "minimum": 0,
+      "type": "integer"
+    }
+  ],
+  "description": "For 'tween': end value — {x,y} for property 'position', 0-255 for 'opacity'."
+}

addedOutput schema / properties / frames

Added value: +{
+  "description": "Only present for 'tween' and 'oscillate': one entry per frame touched, ascending.",
+  "items": {
+    "additionalProperties": false,
+    "properties": {
+      "frame": {
+        "type": "integer"
+      },
+      "opacity": {
+        "type": "integer"
+      },
+      "x": {
+        "type": "integer"
+      },
+      "y": {
+        "type": "integer"
+      }
+    },
+    "required": [
+      "frame"
+    ],
+    "type": "object"
+  },
+  "type": "array"
+}

Changed1 schema field changedv0.1.6Sep 9, 2026

changedInput schema / properties / sprite / description

Previous value: -"Sprite filename or id. Omit to use the sprite Aseprite has focused."New value: +"Which sprite: its id as '#7' (what every result reports back, and the only unambiguous form — two unsaved documents are both called 'Sprite'), its filename, or its display name. Omit to use the sprite Aseprite has focused."

First observedv0.1.0Sep 8, 2026

TDQS

A4.3/5.0

Behavior4/5

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

Annotations already declare destructiveHint=true and readOnlyHint=false, so the safety profile is covered. The description adds genuinely useful behavior beyond that: tween/oscillate operate 'in one transaction' and 'fill in any missing in-between cels from the start cel,' disclosing atomicity and side effects. It stops short of stating reversibility or permission needs.

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?

Front-loaded with purpose followed by the op list, then targeted explanations of the less obvious operations. Dense but nearly every sentence carries information an agent needs to disambiguate ops. Slightly long, though not padded.

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 20-parameter, 11-operation tool with an output schema present, return values need not be explained. The description covers the op semantics and transaction behavior well, but leaves a few parameter interactions (sprite selection, toLayer/toFrame pairing) to the schema.

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 70%, so the schema does much of the work, but the description adds real semantic value by mapping operations to intent (move vs link vs tween vs oscillate) and clarifying the opacity/position distinction for tween. It does not document every parameter (e.g. sprite, toLayer, frames) but complements the schema well.

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?

States a specific verb+resource and defines the concept precisely: 'Manage cels — one layer's image on one frame.' It then enumerates all 11 supported operations, so an agent immediately knows the tool's exact scope. It is clearly distinguishable from siblings like layer or frame.

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

Usage Guidelines4/5

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

Explains what several operations mean and implicitly when to prefer them: 'move' for shifting a limb without redrawing, 'link' for sharing an image across frames, 'tween'/'oscillate' for procedural in-betweens. It gives clear operational context but never explicitly routes the agent away from alternative sibling tools (layer, frame).

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

Deploy Server