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

Annotations already declare destructiveHint=true and idempotentHint=true, so the safety bar is lower, but the description earns credit for explaining the concrete consequence: clip timing is preserved while content re-fits to the new frame size. It does not say whether the operation is undoable or what happens to explicitly positioned/cropped content, which is the main destructive risk left undisclosed.

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 sentence that front-loads the mutation and its field set, then parenthesizes the non-obvious side effect. No filler, no restatement of the title.

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 7-param mutation with no output schema and full annotation coverage, the description covers scope, partial-update semantics, and the resizing side effect. It omits prerequisites (open/active timeline state) and error/failure behavior, which is a moderate gap but not disqualifying.

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; the description adds real semantic meaning by explaining that changing fps/width/height rescales content rather than retiming clips — information the terse schema lines ("Optional new frames per second.") do not convey. It adds nothing about token/projectId/timelineId, but the schema already covers those.

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 (updates) plus the exact resource (a timeline) and enumerates the mutable fields (fps, width, height, name), including the rename case. The resource-level framing separates it cleanly from set_clip_properties and update_motion_composition without needing 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?

"Only provided fields change" implies the partial-update usage pattern, and "and/or" signals fields are optional and combinable. However, no alternatives, prerequisites, or when-not-to-use cases are named (e.g., whether the timeline must be open first, or when to prefer create_timeline/duplicate_timeline instead).

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