design_update_fill

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

With no annotations, the description carries the full burden and it does disclose the key behavior that partial strategy objects are merged with the existing strategy. It omits whether other fields are replaced, whether the target must already be a fill layer, or what happens on an invalid layerId.

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 short sentences with the mutation scope front-loaded. The clause 'without replacing everything' slightly overlaps with the following merge statement but still earns its place as emphasis.

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 an eight-parameter mutation with no annotations and no output schema, the description covers merge semantics but not replacement semantics for shading/shadingAffects, error behavior, or prerequisites. It's adequate only because the schema is fully annotated.

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 coverage is 100%, so all eight parameters are already documented in the schema, including the strategy merge note. The description adds only a restatement of the merge behavior, not new format or constraint detail.

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?

States a specific verb plus resource: modify properties on an existing painting:fill layer, partial update semantics. It doesn't name a contrasting sibling such as design_update_layer, so an agent still has to infer which update tool applies to fill layers.

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 phrase 'without replacing everything' implies this is the tool for partial edits rather than wholesale layer replacement, but no explicit when-to-use or when-not-to-use guidance is given relative to design_update_layer or design_update_pattern.

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