Generate MP4 videos and SRT subtitles from an edit spec for test-session walkthroughs, returning path, duration, frames, size, captions, and optional thumbnails.
Render spec to MP4 (+SRT) -> {path,duration,frames,size_mb,srt,thumbs}.
| Name | Required | Description | Default |
|---|---|---|---|
| out | No | output .mp4 path | |
| spec | Yes | edit spec object, JSON text, or .json path | |
| thumbs | No | also return one image tiling 4 thumbnails | |
| preview | No | 960x540@15fps fast draft |
Changes observed during successful MCP inspections.
v0.1.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description must carry the full behavioral burden. It discloses the return object shape and mentions optional SRT generation, but it does not explain side effects, file writes, overwrite behavior, permissions, or runtime characteristics of a render operation.
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 compact line with no wasted words. It front-loads the verb and artifact, then lists the return keys, making it highly efficient.
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 4-parameter render tool with no annotations and no output schema, the description is only minimally complete. It partially compensates for the missing output schema by listing return fields, but it omits critical behavioral and usage context needed for confident 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 description coverage is 100%, so the input schema already documents every parameter. The description adds little beyond restating that it renders a spec and outputs MP4/SRT, which is baseline adequacy rather than added semantic value.
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 a spec to MP4 and optionally SRT. The output shape is also given, so an agent can tell what the tool produces. However, it does not explicitly differentiate this tool from any sibling, so it falls short of a 5.
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 provides no guidance about when to use this tool, when not to use it, or which alternatives exist among the sibling tools. It simply states what the tool does, leaving usage context entirely to inference.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.