set_fill_color

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

No annotations are provided, so the description must fully disclose behavior. It states that the tool sets the fill color but fails to mention key details: whether it replaces existing fills, handles multiple fill slots, or requires specific permissions. The schema already documents the RGBA parameters, but the description does not clarify that the color components are normalized (0-1) or that 'a' is optional. Missing behavioral context for a mutation tool.

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?

The description is a single sentence that is concise but contains a grammatical error ('can be TextNode or FrameNode' could be interpreted as the tool being a node). It lacks front-loading of key information and could be restructured for clarity without significant length.

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 5 parameters and no output schema, but the description does not explain the return value (presumably success/void) or provide complete usage context. It does not mention that the color values must be in 0–1 range, which the schema already specifies, but the description should re-emphasize this. The description also does not differentiate from similar fill tools, leaving the agent underinformed.

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?

The input schema covers all 5 parameters with descriptions, types, and min/max constraints. The description adds no additional meaning beyond 'fill color'—it does not explain the RGBA values, that 'a' is optional, or that the color is normalized. With 100% schema coverage, the description does not need to repeat details, but it misses an opportunity to clarify the color format.

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?

The description clearly states the action 'Set the fill color' and the resource 'a node in Figma'. It specifies that the node can be a TextNode or FrameNode, but the grammar is slightly awkward and could be more precise (e.g., 'The node can be a TextNode or FrameNode'). It distinguishes from sibling tools like set_stroke_color by mentioning 'fill'.

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?

The description provides no guidance on when to use this tool versus alternatives like set_image_fill or set_gradient_fill. It does not indicate which node types are unsupported or when to prefer this over other fill methods. The mention of TextNode and FrameNode is the only contextual hint, but not enough to guide selection among many fill-related siblings.

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