Extract frame

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

No annotations are provided, so the description carries the full burden. It states the action and output ('save... as an image') but does not disclose edge cases, side effects, or requirements beyond that. This is adequate but lacks behavioral depth.

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 two sentences, front-loaded with the primary action, and contains zero filler. 'Good for previews and cover images' adds useful purpose without verbosity.

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 video-processing tool with fully documented parameters and no output schema, the description adequately explains purpose and result. It could mention default behavior or alternatives, but the combination of description and schema is enough for correct invocation.

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 100%, so parameters are already fully documented. The description adds no additional parameter semantics, which is acceptable per the baseline of 3 when the schema covers everything.

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 and resource: 'Save a single frame of the video as an image (thumbnail/still).' It clearly identifies the tool's function and distinguishes it from siblings like sample_frames by emphasizing 'single frame.'

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 'Good for previews and cover images' provides clear context for when to use the tool. It does not explicitly mention alternatives or when not to use it, but the use cases are sufficient.

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