ae_create_subtitle

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

With no annotations, the description must carry the behavioral burden. It clearly discloses the default white-text-with-black-stroke styling, the absolute behavior of not adding a background bar unless background_bar=true, and the requirement of explicit user intent. This prevents a common hallucinated default that a caption tool adds a black plate.

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?

Three sentences, each earns its place: the purpose, the critical default behavior, and the routing guidance. No redundancy or filler.

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?

Covering the most decision-critical behaviors (no bar by default, explicit-user-ask requirement, solid alternative) alongside schema-covered required parameters makes this adequate. It could add a bit more around barOpacity/fade semantics and what the operation returns, but those gaps are not blocking for correct invocation.

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 62%, leaving y, fade, font, name, fontSize, and barOpacity undocumented. The description adds meaningful default-style context but does not explain those undocumented parameters or map defaults to specific fields beyond fillColor/background_bar implications, so it only partially compensates for the schema gap.

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 opens with a specific verb and resource — 'Add a subtitle/caption text layer' — and further differentiates it from the common alternative of creating a solid for captions. This makes it easy to distinguish from generic siblings like ae_create_layer.

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?

It explicitly says 'Prefer this over solids for captions,' which gives the agent a clear rule for when this tool is the right choice relative to an alternative. It doesn't discuss exclusion cases or compare to ae_create_layer, but the caption-specific wording supplies enough context.

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