Burn subtitles into video

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

With no annotations, the description must carry the behavioral burden; it usefully discloses that output is a new MP4 (source not modified in place) and that paths are sandboxed to ~/Videos. It omits key write-tool behavior: whether an existing output file is overwritten, what happens on invalid SRT or codec failure, and processing time for long videos.

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, zero filler, with the core action front-loaded and the path constraint immediately after. Nothing to cut and nothing buried.

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 3-parameter mutation with no annotations and no output schema, the description covers the action, the output type, and the directory restriction. It stops short of overwrite semantics, failure modes, and what is returned (e.g. path to the new file), which an agent needs before invoking a write tool.

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 0%, so the description must compensate; it does add meaningful semantics — 'subtitles' is an SRT file, 'output' is an MP4, both constrained to ~/Videos. It still leaves path form ambiguous (absolute vs relative to ~/Videos, filename vs full path) and doesn't map 'input' explicitly, so compensation is partial.

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?

States a specific verb and resource: 'Render an SRT subtitle file permanently into a video' with the outcome 'saves a new MP4'. The distinction from siblings (video_probe, trim_video, extract_audio) is obvious by operation, but the description never names or contrasts them, so it sits at a clear-but-undifferentiated 4.

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 operational constraint 'Both files and output must stay in ~/Videos' is a genuine usage rule an agent needs before calling. However there is no when-to-use/when-not guidance, no prerequisites (e.g. ffmpeg), and no statement about re-running or overwriting, so usage is only implied.

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