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set_image_fill

Destructive

Replace a Figma node's fill with a PNG, JPEG, GIF, or WebP image supplied as base64, with WebP and unsupported inputs normalized to PNG locally.

Instructions

Replace a node fill with a PNG, JPEG, GIF or WebP supplied as base64. WebP and unsupported decodable inputs are normalized to PNG inside the local Figma plugin.

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": {
      "nodeId": "<nodeId>",
      "base64": "<base64>"
    },
    "name": "set_image_fill"
  }
}

Input Schema

Name	Required	Default
`base64`	Yes
`nodeId`	Yes
`scaleMode`	No	FILL
`sourceMimeType`	No

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.6.4Sep 13, 2026

TDQS

B3.4/5.0

Behavior3/5

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: WebP and other decodable inputs are normalized to PNG locally in the plugin. However, it doesn't state that the existing fill is replaced/overwritten or what happens on decode failure, so it stops short of rich behavioral disclosure.

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

Conciseness5/5

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

Two sentences, zero filler, and the primary action is front-loaded with the normalization caveat second. Every clause earns its place.

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

Completeness3/5

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

For a destructive, 4-parameter mutation with no output schema, the definition is adequate but thin: it leaves scaleMode, nodeId expectations, and failure/overwrite behavior unexplained, and there is no return-value note. The normalization disclosure is the one piece of real depth.

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?

Schema description coverage is 0%, so the description carries the full burden. It names the accepted image formats, which partially covers sourceMimeType, but says nothing about nodeId, scaleMode (FILL/FIT/CROP/TILE), or the 16 MB base64 cap. Three of four parameters remain semantically opaque.

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 ('Replace a node fill') plus the exact input form ('supplied as base64'), which implicitly distinguishes it from the sibling set_image_fill_from_path. An agent can tell what the tool does without opening the schema.

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

Usage Guidelines2/5

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

No when-to-use, when-not-to-use, or alternative is given. The base64 wording hints at the split from set_image_fill_from_path, but the description never says to prefer the path variant when a file is on disk, leaving routing to inference.

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