Burn in captions

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

The description adds valuable behavioral context beyond the weak annotations (all false). It explains that colors are converted internally from hex to ASS's inverted BGR, that the subtitle file is passed to ffmpeg by path to avoid filter graph corruption, and that style overrides replace embedded .ass styles. These are meaningful implementation details that affect usage and expectations.

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 about 100 words across four sentences, each carrying substantive information. It is front-loaded with the primary purpose and then adds relevant details about styling, colors, and path handling. No redundant or filler content. It could be slightly more compact, but every sentence earns its place.

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?

Given the tool's complexity (nested style and encode options, output schema present), the description covers the main function, styling capabilities, the safety of passing by path, and the caveat about .ass embedded styles. It wisely leaves encode option details to the schema. It does not describe the output path behavior or re-encoding implications, but the output schema and shared EncodeOptions mitigate this. Overall, sufficiently complete for a capable agent.

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 67% schema description coverage, the schema already covers many parameters. The description enhances understanding by explicitly listing controllable styling aspects (font, size, fill/outline colour, position, margins) and explaining the hex-to-BGR conversion. This complements the schema descriptions, especially for style-related fields.

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: 'Burn an SRT or ASS subtitle file permanently into the video.' This clearly distinguishes it from sibling tools like text_overlay (which adds text without burning a file) and auto_caption (which generates captions). It immediately conveys the tool's core function.

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 implies when to use this tool (when you need to permanently bake subtitles into the video) but does not explicitly state alternatives or when-not-to-use. The note about .ass embedded styles being overridden is a useful caveat, but there is no direct comparison with sibling tools. Usage context is mostly implied rather than stated.

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