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Aseprite MCP

by MalloyTheDev
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Python
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add_frame

Adds a frame to an Aseprite sprite: appends an empty frame with a duration, or inserts a copy of an existing frame (renumbering subsequent frames).

Instructions

Add a frame: appended when it is empty, inserted when it copies another.

Args:
    duration_ms: Frame duration in milliseconds (default 100).
    copy_from: If given (1-based), duplicate the content of that frame; otherwise the
        new frame is empty and goes at the end. Must name an existing frame: an
        out-of-range number is rejected, not clamped. **A copy is inserted, not
        appended**, so every frame from that point on is renumbered: on a two-frame
        sprite, `copy_from=1` gives three frames whose second is the original first.
        Pass no `copy_from` and the sprite's existing frames keep their numbers.

Returns the new frame number and updated frame count. With `copy_from`, `newFrame` is
where the copy landed, which is also the number the frames after it shifted from.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
filenameYes
copy_fromNo
duration_msNoDefault: 100.

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed8 schema fields changedv0.10.0
    • removedInput schema / properties / copy_from / anyOf
      Removed value: -[
-  {
-    "type": "integer"
-  },
-  {
-    "type": "null"
-  }
-]
    • removedInput schema / properties / copy_from / default
      Removed value: -null
    • removedInput schema / properties / copy_from / title
      Removed value: -"Copy From"
    • addedInput schema / properties / copy_from / type
      Added value: +"integer"
    • addedInput schema / properties / duration_ms / description
      Added value: +"Default: 100."
    • removedInput schema / properties / duration_ms / title
      Removed value: -"Duration Ms"
    • removedInput schema / properties / filename / title
      Removed value: -"Filename"
    • removedInput schema / title
      Removed value: -"add_frameArguments"
  2. First observedv0.7.0

TDQS

A4.5/5.0
Behavior5/5

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

Annotations only give a generic mutation/safety profile (readOnlyHint false, destructiveHint false). The description goes well beyond that by disclosing the frame-renumbering side effect of insertion, with a concrete two-frame worked example, plus the rejection-not-clamp behavior and the exact return contents (newFrame and updated frame count). This is exactly the kind of non-obvious behavioral context the description should carry.

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-loads the core behavior in the opening line, then uses a clean Args structure. It is somewhat verbose and uses bolding for emphasis, but each sentence carries real semantic content (renumbering, rejection semantics, return values) rather than padding.

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?

With no output schema, the description appropriately explains the return values, and for a mutating tool it covers the key side effect (renumbering) and error behavior. The only shortfall is the undocumented required filename parameter, which is left unexplained in both schema and description.

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 only 33% (just duration_ms's default), so the description must compensate, and it does for two of three params: duration_ms default, and copy_from's 1-based indexing, existence requirement, out-of-range rejection and renumbering effect. The required filename parameter is never mentioned in either the schema or the Args list, leaving a small gap.

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 and resource ('Add a frame') and immediately characterizes the two operating modes: appended when empty, inserted when copying. Combined with the copy_from detail, an agent can distinguish this from siblings like duplicate_frame or move_frame without opening a schema.

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?

The description clearly explains the two conditional modes (pass copy_from to duplicate content, omit it to append an empty frame) and warns that an out-of-range value is rejected rather than clamped. It stops short of naming an alternative sibling (e.g. duplicate_frame) for the copy case, so guidance is strong but not fully explicit about when to prefer another tool.

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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