get_frame_at

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

With annotations already marking readOnlyHint and idempotentHint, the description adds meaningful behavioral detail: exact frames are extracted from existing local files, otherwise the nearest cached keyframe is returned and the caption notes this. It also discloses the transcript inclusion and approximate image size, going beyond what annotations capture.

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 compact and front-loaded, starting with the core purpose before covering fallback behavior and output details. Every sentence contributes useful information, though it is slightly longer than the minimum needed.

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?

Given no output schema, the description adequately explains what the agent receives: one image, approximate size, transcript paragraphs, and the keyframe caption caveat. It covers the important edge case of missing local files and gives enough context for a correct call, though it does not discuss failure modes or prerequisites at length.

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 67%, and the description mostly restates that the frame corresponds to a specific time rather than adding new parameter-level semantics. It does connect the default 960 px to the ~100 KB output, but it does not substantially enrich the meaning of video, time, or max_width beyond the schema.

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 ('Look closely at one moment') with a clear resource ('already-watched video') and concrete use cases like reading code, slides, or UI. It also explicitly says it returns one image, distinguishing it from siblings like get_frames or watch_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?

The description conveys a clear context for use: when you need a close, detailed look at a specific moment of a previously watched video. It does not explicitly name alternatives or give when-not-to-use guidance, so it stops short of a 5.

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