get_frame_at

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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds useful behavioral context beyond annotations: supported video sources, dependency on yt-dlp for many platforms, and a return type of a single image. It does not contradict annotations.

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 well-structured and front-loaded: purpose, use case, supported inputs, args, and return value. Every sentence earns its place; the supported-source list is long but necessary, and there is no filler.

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 tool with no output schema, the description adequately states what is returned. It covers supported input types, timestamp format, and use case. Minor gaps remain, such as not explicitly stating the default output is a file path unless returnBase64 is set, though that is covered in the schema.

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%, and the schema contains detailed descriptions for all four parameters including maxWidth and returnBase64. The description repeats only url and timestamp with brief examples, adding little beyond what the schema already provides.

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 opens with a specific verb+resource+scope: 'Extract a single video frame at a specific timestamp.' It clearly differentiates from siblings like get_frame_burst and get_frames by emphasizing a single frame at a precise moment.

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 says it is 'Useful for inspecting what's on screen at a particular moment' and even outlines an AI workflow of reading a transcript and requesting a critical frame. It provides clear context but does not explicitly state when to prefer siblings like get_frame_burst or get_frames.

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