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

Annotations already declare a non-destructive, idempotent, open-world mutation. The description adds no further behavioral context such as what exactly is created, permissions required, side effects on the timeline, or how expectedRevision affects the write. It does not contradict annotations, but it does not enrich them either.

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 a single front-loaded sentence with no filler. However, it is too sparse for a 12-parameter mutation tool with low schema coverage, so its brevity becomes under-specification rather than effective conciseness.

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 12-parameter tool with 25% schema coverage, existing annotations, and an output schema, this description is incomplete. It gives the purpose but omits the parameter meanings and usage context needed to invoke the tool correctly.

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?

With only 25% schema description coverage, the description must compensate for 9 undocumented parameters. It indirectly touches on timelineItemId (optional attachment) and includeSfx (paired with sound), but ignores name, easing, preset, intensity, layerIndex, durationSeconds, and expectedRevision.

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 states a specific verb and resource: 'Add a timed transition effect.' It distinguishes itself from timeline siblings like add_text_overlay or timeline_audio_add by resource type, though it does not explicitly name an alternative. Clarity is high but lacks sibling routing.

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?

There is no when-to-use or when-not-to-use guidance. The phrase 'optionally attached to one timeline item and paired with sound' implies the tool can be used standalone or attached, but this is context about parameters, not selection guidance versus alternatives.

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