Extract text from a video frame region in reading order, returning each line's text and bounding box. Use it to capture on-screen captions or subtitles.
Read all text lines in region at t -> {t,lines:[{text,box}]} in reading order.
| Name | Required | Description | Default |
|---|---|---|---|
| t | Yes | time in s | |
| video | Yes | video path (relative to workdir ok) | |
| region | No | [x0,y0,x1,y1] source px; null=full frame |
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 carries the full behavioral burden. It discloses the return structure and reading order, which is useful, but does not explicitly state that it is read-only, has no side effects, or describe any error conditions or performance characteristics.
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 with zero waste. It is front-loaded with the core action and compactly includes the output shape and ordering constraint, which is valuable given there is no output schema.
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 simple OCR tool with a rich input schema and no output schema, the description provides the essential return format inline. It covers core invocation needs but leaves some behavioral aspects (e.g., error handling, read-only confirmation) implicit.
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 schema already documents all parameters. The description only restates 'region at t' without adding any syntax or format details beyond what the schema provides. Baseline 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 clearly states a specific verb and resource: 'Read all text lines in region at t'. It also defines the output format. However, it does not distinguish this tool from siblings like find_text or track_text, which likely also deal with text extraction.
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?
There is no guidance on when to use this tool versus alternatives such as find_text or track_text. The description only implies usage through the 'at t' phrasing, but does not explicitly state when or when not to choose this tool.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.