Set Fill

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

The description clarifies that this sets a literal fill rather than a style reference or token binding, which is behavioral context beyond the idempotentHint and openWorldHint annotations. It does not disclose overwriting semantics or error conditions, so not a 5.

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?

Two sentences, directly states the purpose and alternatives, with no redundancy. The description is front-loaded and every word earns its place.

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?

For a complex tool with nested image object and multiple modes, the description-plus-schema provides a complete picture. The description supplies the key decision point (literal vs style vs token), while the schema covers technical details and constraints. Minor gap: no mention of node type restrictions or potential errors, but these aren't essential given the schema.

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?

Schema description coverage is 100%, so the schema fully documents all parameters. The description adds a high-level summary of the three modes (color/image/clear) but no additional parameter-specific details beyond what the schema already provides.

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 tool sets a node's fill to a literal RGBA color, an image, or clears it. It explicitly distinguishes from alternatives (node_apply_style, node_bind_variable), making the purpose specific and unambiguous.

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 explicit guidance: use this for literal fills, and directs the agent to node_apply_style for shared styles and node_bind_variable for color tokens. This covers when to use and when-not-to-use scenarios.

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