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

Annotations already declare destructiveHint=true and idempotentHint=true, so the safety profile is covered. The description adds real value beyond that: it discloses optimistic concurrency ('Revision checked') and that the default is a non-committing preview ('dryRun previews by default'), which the annotations alone do not convey.

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?

Two tight sentences with zero filler, and the core operation is front-loaded before the revision/dryRun caveat.

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?

An output schema exists, so return values needn't be explained. But for a destructive, 6-required-parameter mutation with low schema coverage, the description omits the idempotency contract and the meaning of the items array and its limits, leaving notable gaps.

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 only 17% and six parameters are required. The description hints at startSeconds/layerIndex ('explicit times and layers') and expectedRevision ('Revision checked'), but leaves idempotencyKey, items array bounds (1-500), and item id/layer constraints entirely to the schema. It does not compensate for the coverage gap.

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 ('Move selected timeline items') plus the scope of the operation ('explicit times and layers'). It is distinguishable from siblings like update_timeline_clip or batch_update_timeline_clips, though it never names an alternative directly.

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?

The clause 'dryRun previews by default' implies the intended preview-then-commit workflow, but there is no explicit guidance on when to prefer this tool over update_timeline_clip, batch_update_timeline_clips, or editor_items_remove.

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