extract_frame

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

No annotations are provided, so the description carries the behavioral burden. It usefully discloses the output format (PNG), the fact that exactly one frame is extracted, and the accepted timestamp forms. It does not specify whether the PNG is returned directly or saved to a path, but the core behavior is clear.

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 entire description is one front-loaded sentence with no filler. The timestamp examples are compact and immediately useful, and every part of the sentence earns its place.

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 two-parameter tool, the description covers the core action well. However, with no output schema and no annotations, it omits the output destination or return shape, leaving the agent to assume what happens to the generated PNG.

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%, so the baseline is 3. The description adds value beyond the schema by giving concrete timestamp format examples ('90', '1:30', '00:01:30'), which clarifies how the timestamp parameter should be expressed.

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 clearly states the verb and resource: 'Grab a single frame from a video as a PNG image.' It also specifies the output format, which distinguishes it from sibling tools like extract_audio, trim_video, or create_gif.

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 intended use is implied—extract one still image at a timestamp—but there is no explicit when-to-use guidance or mention of alternatives. An agent must infer when to prefer this over create_gif or trim_video.

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