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

Richly discloses behavior beyond the annotations: new ids for timeline/tracks/clips/transitions, clip links preserved inside the copy, nested timelines copied by default, motion compositions and media merely referenced, original untouched and still active, and one undo removes the copy. This is fully consistent with destructiveHint=false and readOnlyHint=false.

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?

Front-loads the purpose, then layers the copy semantics economically. It is on the longer side with several clauses, but nearly every sentence carries information an agent needs to call it correctly.

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?

No output schema, but the description states the return shape ({timelineId, name, clips, nestedCopies?}) and covers the copy semantics, defaults, and undo behavior. Nothing an agent needs to invoke it safely is missing.

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 100%, so the baseline is 3, but the description adds real meaning for includeNested — explaining that copying nests means editing a nest in the original does not alter the backup — which goes beyond the schema's terse phrasing.

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 ('Copy a timeline under a new name') and immediately clarifies it is a DEEP copy versus a plain new timeline, distinguishing it from create_timeline without the agent needing to open schemas.

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?

Gives concrete when-to-use scenarios — a backup before a review round, or a variant to experiment on — so the agent knows the intent. It does not explicitly name create_timeline or open_timeline as alternatives or state when NOT to use it, keeping it below a 5.

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