add_text_overlay

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

Beyond annotations, the description reveals that the tool uses the Captions/Subtitle API, places text on a caption track at the default subtitle position, and notes the API limitation. This adds valuable behavioral context, though it could mention side effects or error cases.

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?

Two sentences efficiently deliver the core purpose, important caveat, and alternative approach without extraneous details.

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 void operation with no output schema, the description explains the behavior (captions track, default position) and addresses the main limitation, making it sufficient for an agent to understand the outcome.

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 provides 100% coverage with descriptions for all 4 parameters. The description adds little beyond clarifying that start_seconds defaults to 0 and caption_format defaults to 'subtitle', but this is already implied. Baseline is appropriate.

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 explicitly states the action ('Add a subtitle-style text overlay') and the target ('active sequence'), distinguishing it from freeform titles by noting the API limitation and suggesting an alternative.

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 explains when to use this tool (for subtitle-style overlays) and when not to use it (for freeform titles, suggesting a PNG approach instead), guiding correct selection.

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