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

Beyond the readOnlyHint annotation, the description details the precise return structure (clips per track, captions, total duration) and confirms 'Free, read-only.' It adds substantive behavioral context about what the agent will receive, going beyond the annotation.

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 efficiently packed: it lists output fields first, then gives usage context, and ends with a behavioral note. No redundancy, and the critical info is front-loaded.

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 it's a read-only tool with no output schema, the description fully explains what is returned, when to use it, and how to proceed after. It covers all necessary details for correct invocation.

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 schema has 0% description coverage for parameters, and the description does not clarify the roles of video_id and project_id. It only says 'Read the FULL timeline of a video' without explaining which identifier is required or how they relate. This fails to compensate for the lack of schema documentation.

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 uses a specific verb ('Read') and resource ('FULL timeline'), enumerates the exact fields returned (clip_id, asset_id, duration_sec, etc.), and explicitly contrasts with get_state, making it unambiguous and distinct from siblings.

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 states when to use this tool ('before editing') and explicitly names the alternative ('get_state does not include durations'), giving the agent a clear decision rule and post-use guidance ('Reference clips by clip_id afterwards').

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