chroma_key

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

With no annotations, the description must disclose behavior itself. It only states the action and provides no details on whether the clip is mutated or a new clip is returned, how the masked area is treated (e.g., becomes transparent), or any potential side effects. This is insufficient for a tool with no annotation support.

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?

A single, concise sentence that immediately states the purpose and key alias. There is no filler or redundant information, making it optimally front-loaded.

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?

While the output schema and parameter schema are rich, the description lacks crucial context about when to use the tool (versus alternatives) and behavioral outcomes. With no annotations, the description alone does not give an agent enough confidence about side effects or return behavior.

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 input schema already documents all four parameters with meaningful descriptions (e.g., color_rgb, stiffness, threshold). The tool description adds no extra parameter semantics beyond the schema, so the baseline score of 3 is appropriate given the high schema coverage.

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 uses a specific verb ('Mask') and resource ('a color in a video clip') plus the clarifying parenthetical '(chroma key / green screen)'. This clearly distinguishes it from sibling color tools like adjust_colors or to_grayscale.

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?

No guidance is given on when to use this tool versus alternatives such as adjust_colors or to_grayscale. The context is implied by the 'green screen' mention, but there are no explicit usage scenarios or exclusions.

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