obs_scene_item_blend_mode

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It explains the visual effects of each blend mode, how the mode depends on stacking order, and why an item at index 0 might appear unchanged. It does not discuss return shape or error behavior, but the core runtime behavior is well covered.

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 front-loaded with a one-sentence purpose, then organizes additional detail by theme: mode semantics, z-order interaction, and read behavior. Every sentence contributes meaningful information with no repetition of schema contents or filler. The length is justified by the complexity of the blend-mode concepts.

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 description covers the main behavioral nuances: read versus write, blend-mode semantics, z-order dependence, and the index-0 pitfall. It does not formally describe the output of a read, and there is no output schema to fill that gap, but the tool's domain is narrow and the provided guidance is enough for an agent to invoke it correctly in most cases.

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%, establishing a baseline of 3. The description adds substantial meaning beyond the schema by explaining what each blend mode does (additive/screen dropping black, multiply/darken dropping white), and clarifies that omitting blendMode means a read. This elevates the parameter documentation beyond the bare enum list.

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 opens with a specific verb-resource pair: 'Read or set how a scene item composites with the layers under it.' This distinguishes it from sibling scene-item tools like transform, order, or lock, and clearly identifies the property being manipulated.

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 gives clear guidance on when to use the tool and how to use it correctly, including the 'Omit blendMode to read' pattern and the z-order interaction caveat. It does not name explicit alternatives, but no direct sibling offers blend-mode functionality, so the contextual guidance is strong.

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