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

The non-mutating claim reinforces the existing readOnlyHint=true / idempotentHint=true / destructiveHint=false annotations but adds nothing they don't already convey. Nothing is said about expectedRevision conflict handling, snapToFrame effects, or what a preview response contains beyond the read-only guarantee.

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 tight sentence with the preview constraint front-loaded. No filler, nothing wasted.

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 and rich annotations lower the disclosure burden, but with five required parameters at 40% schema coverage the description leaves key inputs (expectedRevision, snapToFrame) unexplained for an operation whose correctness depends on them.

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 40% across five required parameters. The description conveys that a timeline item is split but does not explain expectedRevision (optimistic concurrency), snapToFrame, or splitAtSeconds semantics, so it fails to 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?

Clear specific verb (preview splitting) plus resource (one timeline item) and an explicit scope constraint (without changing the project). This implicitly separates it from the sibling timeline_split_apply, though it never names that sibling 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 word 'preview' and 'without changing the project' imply this is a safe dry-run to be used before applying a split, but the description never states when to use it versus timeline_split_apply or timeline_trim_preview. Usage is left to inference.

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