set_blend_mode

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

Annotations only indicate non-read-only and non-destructive. The description adds valuable context: the effect is only on compositing, not fills, the PASS_THROUGH nuance, and the return shape { ok, nodeId }. It doesn't cover error handling or preconditions, but for a simple setter this is reasonable. No contradiction with annotations.

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?

Three concise, front-loaded sentences: main purpose, special-case caveat, and return type. Every sentence adds relevant information with no filler.

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 simple 2-param setter with 100% schema coverage and no output schema, the description covers return value and a key constraint. Missing error behavior and full enum list, but the provided details are sufficient for typical invocation. This is well above the minimum viable.

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 already describes both parameters, so baseline is 3. The description enriches blendMode with concrete examples and a special case (PASS_THROUGH), adding meaning beyond the schema. nodeId is clear from schema, and return info is extra but not param-specific.

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?

Description states a specific verb+resource: 'Set how a node composites with the layers beneath it.' It lists concrete blend mode values and explicitly differentiates from siblings like set_fills and set_opacity, making the tool's scope 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?

Provides clear when-to-use guidance: 'use set_fills or set_opacity for those' directly names alternatives for related actions, and it explains a constraint (PASS_THROUGH only on groups/frames), helping an agent choose this tool appropriately.

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