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

Annotations declare readOnlyHint=false and idempotentHint=false, but give no sense of what actually happens. The description fills that gap: the URL is short-lived, single-device, browser-openable, and the server transcodes the live stream to MJPEG on the fly. It doesn't say whether repeated calls spawn multiple transcodes or how/whether a stream is stopped, which is the remaining unknown for a non-read-only tool.

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?

Three tight sentences, front-loaded with the core capability, then the return-value shape, then the intended use. No filler or restatement of the title.

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?

With no output schema, the description correctly explains the return value (a short-lived viewer URL) and the required follow-up action (open it directly in a browser). The only gaps are operational details an agent might want, such as URL lifetime and whether the stream needs to be torn down, which is a minor omission rather than a blocking one.

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?

Only one parameter (udid) with 100% schema description coverage ('Device serial number (UDID)'), so the schema carries the meaning. The description adds only that the resulting URL is bound to a single device, not new syntax or format detail for udid. 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?

Specific verb (Get) plus resource (LIVE video-stream link) and scope (Android device, single-device, real-time). It explicitly contrasts with device_screenshot ('one frame'), so the agent can distinguish it from the nearest sibling without opening either schema.

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?

Gives a clear use case ('Use this to let a person supervise what the agent is doing on the device') and distinguishes the live-stream case from the one-frame screenshot case. It stops short of stating when-not to use it (e.g. for automated analysis, use device_screenshot/MJPEG instead) or any device prerequisites.

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