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

Annotations already cover the read-only/idempotent/non-destructive profile, and the description adds real behavioral context on top: a 30-minute duration cap with refusal semantics, caching so a second call is free, evenly spaced key frames, and the meaning of a `partial` transcript. That is exactly the beyond-annotation detail the dimension rewards.

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?

Four dense sentences with the core action front-loaded, then limits, caching, caveat, and sibling routing in descending order of importance. No filler and no repetition of the annotation flags.

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?

With no output schema, the description carries the return-value burden and does: transcript text plus images of key frames for video. Combined with the duration cap, caching note and truncation caveat, an agent has everything needed to call it and interpret the result.

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 file_id, max_chars, max_frames and in_workspace are already documented, including '0 = transcript only' for frames; the description adds little parameter detail beyond that. It also refers to a `partial` field that is not an input parameter, which reads as a response flag rather than a call argument and could momentarily confuse which value the agent controls.

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?

Specific verb and resource: understands an AUDIO/VIDEO file and returns the spoken text as a transcript plus key frames for video. It also explicitly routes other media types elsewhere ('For images use files.get_base64, for text and documents files.read'), so an agent can separate it from files_read/files_get_base64 without opening any schema.

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?

States the use case (voice note, recording, clip) and names the alternative tools for images and documents with the condition that selects them. It also gives a hard eligibility rule: files over 30 minutes are refused, so an agent knows when this tool will fail before calling it.

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