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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered; the description adds genuinely new behavioral context by disclosing stream-copy (no re-encode) and keyframe-snapped cut points, which tells the agent the output is lossless but frame-imprecise. It stops short of describing the return payload (e.g., base64 video) or size limits.

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?

A single front-loaded clause plus an em-dash qualifier; the operation comes first and the fidelity caveat second, with zero 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 three-required-parameter transform with no output schema, the definition covers what the tool does and its precision tradeoff, but leaves the agent guessing about input encoding/size constraints and the shape of the returned trimmed video.

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 0%, so the description must compensate for all three parameters. It partially does: "time range" maps to startSeconds/endSeconds and the keyframe-snapping note usefully warns that those boundaries are approximate, but it says nothing about fileBase64 expectations, units, end-inclusivity, or out-of-range behavior.

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?

States a specific verb and resource ("Trim a video") plus the scope ("to a time range"), which cleanly separates it from video_compress, video_convert, and video_merge in the sibling list. An agent can identify the operation without opening the 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?

Usage is only implied by the verb — trim when you need a sub-range of a video. There is no explicit when/when-not guidance, no mention of alternatives such as video_convert for format changes or video_compress for size reduction, and no prerequisites stated.

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