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

Annotations already declare write (readOnlyHint=false), non-destructive, and non-idempotent, so the safety profile is covered. The description adds two genuinely useful behavioral facts: the call is strictly project-scoped and it returns the project identity with the result. It still doesn't say what the operation mutates or whether a project must be open, so it earns only partial credit.

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 front-loaded 'PROJECT-SCOPED' clause is well-placed, but the remaining two sentences are opaque metaphor ('a meta beat', 'explaining itself') that consume space without conveying actionable information.

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?

A non-idempotent write tool with 7 undocumented parameters and no output schema needs the description to carry meaning, and it largely doesn't — parameter behavior, target of the edit, and result shape beyond 'project identity' are all unstated.

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?

Seven parameters with 14% schema coverage; only project_id is described. The prose ('cut, graphics, devices, world, camera, sound lanes, true names') gives no meaning to start, end, title, follow, id, or the position enum. The description does not compensate for the schema gap at all.

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 tool name and title say 'Add breakdown', but the description never states plainly what is added or where — it instead riffs on what a breakdown conceptually is ('the edit explaining itself', 'a meta beat'). Against siblings like add_title_card or add_captions, an agent cannot tell what asset this creates or how it differs. The 'PROJECT-SCOPED' prefix is the only concrete framing.

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 relative to the many add_* siblings, nor prerequisites beyond the project scoping note. The scoping directive ('acts only on the explicit project_id... never used to guess') is useful but is about parameter mechanics, not tool selection.

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