grab_frames

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

With no annotations, the description carries the full behavioral burden and does so well: it discloses the ffmpeg dependency, non-silent failure behavior, page-cache separation for multi-part videos, quality limitations for reading numbers, and the returned {sheet, grid[]} structure.

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 content is front-loaded and organized with clear sections, and most sentences earn their place. Some warnings and emphasis are repeated, making it slightly longer than necessary.

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 frame-extraction tool with no annotations and an output schema present, the definition provides enough context to call it correctly: trigger conditions, quality guidance, multi-part handling, dependency behavior, and return-value interpretation.

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%, so the description must compensate. It richly explains quality and page semantics, including practical consequences, and implies at_seconds usage around the error timestamp, but bvid and the exact array format of at_seconds are not explained.

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 states a specific action — extracting frames on demand — and sharply scopes it to cases where subtitle/transcript errors affect understanding. It also distinguishes the tool from the anti-pattern of extracting frames for the whole video.

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?

It gives explicit when-to-use criteria (numbers, proper nouns, parameter names whose misreading changes the conclusion) and a clear when-not-to-use warning against full-video extraction. It does not explicitly name an alternative sibling tool, so it falls 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.