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

With annotations only covering the safety profile (not read-only, not destructive, not idempotent), the description adds the operationally critical details: the page self-authenticates for ~5 minutes, keeps working for 30 minutes, reconnects after a drop, and is bound to 'the user currently holding this device -- share with care'. It also states the view's lifetime is the device session, which explains the non-idempotent/non-destructive hints.

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?

Front-loaded with the purpose and the key delivery instruction, and nearly every clause carries real information. It is nevertheless dense for a one-parameter tool, with overlapping lifetime statements (5-minute auth, 30-minute page, session-length view) that could be tightened.

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?

There is no output schema, but the description enumerates the returned JSON fields and explains what each is for (viewerUrl to hand to the user, websocketUrl as a raw RFB stream with subprotocol and no password, width/height as device pixels matching device_tap coordinates). Nothing an agent needs to call or interpret the result is missing.

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 coverage is 100% for the single udid parameter, so the schema already carries its meaning. The description's coordinate/lifetime notes concern the return payload rather than the input, so it adds nothing new about parameters; baseline 3 applies.

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 ('Open a live, interactive view of an Android device') and immediately scopes who it is for ('for the USER -- they see the screen and can tap, swipe, scroll and type'). It is clearly distinguishable from android_vnc_snapshot, which the description explicitly reserves for the agent looking at the screen itself.

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 explicit routing: 'GIVE THE USER viewerUrl (or open it in the IDE's built-in browser)' for the interactive case, and 'To LOOK at the screen yourself, use android_vnc_snapshot' for the alternative. It even pre-empts a related tool's misuse by noting android_vnc_close 'has nothing to release'.

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