Create layer mixer

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

The description goes well beyond the annotations (readOnlyHint=false, openWorldHint=true, destructiveHint=false) by disclosing specific behaviors: it creates a baseCOMP, uses Select TOPs, auto-creates demo sources when fewer than two inputs, outputs a Null, and returns a detailed JSON summary including errors, warnings, and a preview image. This gives the agent a clear mental model of what happens.

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 four sentences, each packed with essential information: what it does, how blend modes work, the Select TOPs and demo behavior, and the return format. There is no fluff or redundancy; it is well-structured and front-loaded with the primary purpose.

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?

Even without an output schema, the description fully explains the return value (summary plus JSON block with paths, controls, errors, warnings, and preview). It also covers edge cases (fewer than two inputs) and the downstream use (Null ready for post-processing). Given the tool's moderate complexity, this is complete.

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 schema already documents all four parameters with 100% description coverage, so the baseline is 3. The description adds extra meaning by explaining the effect of the 'blend' parameter ('crossfade makes an A/B Cross TOP with a Crossfade knob; any other blend mode composites the inputs') and the demo-source fallback for the 'inputs' parameter. This adds value beyond the schema, but not dramatically so, hence a 4.

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 and resource: 'Build a VJ-style layer mixer: combine source TOPs into one output. Creates a new baseCOMP under parent_path.' It clearly distinguishes this tool as a mixer for visual layers, with the key output being a baseCOMP. This is distinct from sibling tools like create_layer_stack or create_visual_system, and the scope is 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 clear context for when to use the tool: for VJ-style mixing of TOPs, with specific blend modes (crossfade vs. composite). It also explains the output readiness ('Output is a Null ready for post-processing or setup_output'). However, it doesn't explicitly state when not to use it or name alternative tools, so it stops short of a full 5.

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