chroma_key

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

With no annotations the description must carry the full behavioral burden. It usefully discloses the resulting alpha output and container/codec options (.mov ProRes 4444, .webm VP9, PNG sequence) and a speed characteristic, but says nothing about overwrite behavior, quality tradeoffs, or how 'fast first pass' differs in fidelity.

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 tight sentences, front-loaded with the core operation followed by the output-format and speed detail. No wasted words, though the brevity comes at the cost of explaining any of the six parameters.

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 six-parameter, no-annotation, no-output-schema mutation tool with 0% schema coverage, the description is too thin. It gives output formats and a speed hint but leaves keying parameters and the meaning of the returned alpha entirely undocumented.

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 description coverage is 0% and there are six parameters (blend, color, despill, similarity, input, output). The description explains none of the tuning parameters and only loosely implies the output format, so it fails to compensate for the schema's complete lack of parameter documentation.

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 names a specific operation (green/blue screen key) and its result (clip with alpha), and even enumerates the supported output codecs. It does not explicitly name a sibling, but 'a fast first pass' implicitly separates it from a slower, higher-quality matte tool.

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 'A fast first pass' implies a quick/preview use case, hinting that a more thorough sibling (e.g. matte_external) should be used for final quality. However, there is no explicit when-to-use/when-not guidance or named alternative, leaving the agent to infer.

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