Burn in subtitles

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

With no annotations, the description carries the burden of behavioral disclosure. The word 'Permanently' is a meaningful disclosure that subtitles become part of the video and cannot be removed later. However, it does not state what happens when output_path is omitted (e.g., whether the input is overwritten) or any codec/performance considerations.

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 sentence, front-loaded with the core action, and contains no unnecessary words or filler. It is appropriately terse.

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?

The tool is relatively simple and the schema covers all parameters, but the lack of annotations and output schema means the description should compensate. It does not clarify default output behavior or differentiate from add_text_overlay, leaving some ambiguity for an AI agent. Still, it provides a complete high-level understanding for basic use.

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 100% (all four parameters have descriptions). The description text adds no additional parameter semantics beyond what the schema already provides, so the baseline score of 3 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 uses a specific verb ('render') and specifies the resource ('subtitle file onto the video frames'), clearly distinguishing it from sibling tools like add_text_overlay. It also defines the subtitle file formats (.srt or .ass).

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 clearly implies when to use this tool (to permanently burn subtitles into video frames) but does not explicitly mention alternatives or exclusions. It does not compare with add_text_overlay or note cases where soft subtitles would be preferable.

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