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

Annotations already declare readOnlyHint=false, idempotentHint=true, and destructiveHint=false. The description adds the constraint about providing at least one field, but no additional behavioral traits like return formats or revision checking. It is consistent with annotations but does not go beyond them.

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?

The description is two sentences, front-loaded with the core purpose and followed by a necessary usage constraint. Every word earns its place, and it is appropriately compact for the tool's complexity.

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?

Given the 11-parameter schema and output schema presence, the description covers the key functional fields and distinguishes from similar tools. It omits explicit guidance on when to use this tool versus batch_update_timeline_clips, but the 'one' qualifier mitigates this. Overall, it is sufficiently complete for a concise tool description.

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 27%, but the description names several updatable fields (start, duration, trim, layer, ignored state, blurred background), providing some semantic guidance. It does not elaborate on parameter-specific details like the meaning of trimStart vs trimEnd or expectedRevision, leaving a gap for 8 undocumented parameters.

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?

The description clearly states the action ('Update') and the resource ('one timeline item'), and lists specific attributes ('start, duration, trim, layer, ignored state, or blurred background'). It distinguishes from the sibling 'batch_update_timeline_clips' by emphasizing 'one' timeline item.

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 description implies usage for single-item updates by saying 'one timeline item' and provides a key prerequisite: 'Provide at least one field to update besides timelineItemId.' It does not explicitly name alternatives or exclusions, but the sibling tool name suggests batch usage, making the context clear.

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