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

The annotations already convey readOnlyHint=true, idempotentHint=true, and destructiveHint=false. The description adds the non-destructive framing 'without touching it' and describes the output, but does not add deeper behavioral traits such as runtime, authorization needs, or limitations. This is adequate, but it mostly reinforces what annotations already state.

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 front-loaded with the operation and return values, then gives usage rationale. It is a little more conversational than strictly necessary, with repeated emphasis on the frames and the guessing problem, but every section earns a place and helps an agent use the tool correctly.

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?

Without an output schema, the description does a strong job of enumerating the key return contents: length, frame rate, resolution, audio presence, shot boundaries, and labeled frame timecode. It also explains the downstream flow. A dedicated return-type description would make it fully complete, but the available details are enough.

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?

The input schema already covers the single parameter video_url with the description 'link to video', so schema coverage is 100%. The tool description does not add much beyond that: it does not specify accepted formats, URL handling, or validation rules, so it stays at the schema-dependent baseline.

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 is specific: it says the tool watches a video and measures it, and lists exact outputs such as length, frame rate, resolution, audio presence, cut times, and a frame per shot. It also distinguishes itself from sibling tools by showing how its outputs feed into score_my_video and find_soundtrack.

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 explicitly states when to use the tool: 'Use this before find_soundtrack when the user has asked for music or a soundtrack, provided a video, but has not said how long it is.' It also gives concrete downstream instruction that the frame timecode should be passed as a section boundary to score_my_video.

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