start_video_stream

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

No annotations are provided, so the description bears full responsibility for behavioral disclosure. It mentions opening a native ffplay window and requiring an active scrcpy session, but fails to describe side effects (e.g., blocking behavior, resource usage, what happens if already streaming) or how to stop the stream.

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 two sentences, with the primary purpose first and a necessary prerequisite second. It is concise and front-loaded, though the second sentence could be slightly more integrated.

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 no annotations, no output schema, and two well-described parameters, the description covers the basics but omits important context: how to stop the stream (via stop_video_stream), what the stream URL is, and whether the ffplay window must be manually closed. It is minimally adequate.

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?

The input schema already provides full coverage (100%) for both parameters (serial, port) with clear descriptions. The tool description adds no additional meaning beyond what the schema states, so it does not improve parameter understanding.

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 the tool starts an HTTP MJPEG video stream of the device screen, using a specific verb and resource. It implicitly distinguishes from siblings like screenshot (single image) and screen_record (file recording) by mentioning the stream and ffplay window.

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 mentions a prerequisite ('Requires an active scrcpy session') but does not provide explicit guidance on when to use this tool versus alternatives like screen_record_start or screenshot. There is no mention of when not to use it or trade-offs.

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