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

Annotations already declare readOnlyHint=true, idempotentHint=true and destructiveHint=false, so safety is covered structurally. The phrase 'without changing the project' usefully reinforces the no-op guarantee, but the description says nothing about what the preview returns or how deltas are validated.

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 sentence with no filler; the key constraint (no project change) is stated immediately. It is efficient, though arguably too short given the six required parameters.

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 six required parameters at 33% schema coverage, an output schema covering return values, and annotations covering safety, the remaining gap is parameter meaning and the reconciliation/revision requirement. The description addresses none of that, leaving the agent to guess at delta semantics.

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 only 33%, so the description carries the burden, yet it explains none of the unclear parameters. It does not clarify that trimStartDeltaSeconds/trimEndDeltaSeconds are signed deltas (negative = extend?), nor what snapToFrame or timelineItemId control.

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 (preview) plus the exact action (trimming or extending), the scope (one timeline item), and the crucial non-mutation constraint. This implicitly distinguishes it from timeline_trim_apply, though it never names that sibling explicitly.

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: 'Preview ... without changing the project' suggests a dry run before timeline_trim_apply, but there is no explicit when-to-use, no stated prerequisites (e.g. needing a valid expectedRevision), and no named alternative.

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