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

Annotations only declare the safety profile (readOnlyHint=true, destructiveHint=false, openWorldHint=false); the description adds substantial context beyond that: a few-frames-per-second screen feed, the Take control hand-off, the privacy guarantee that 'what they type there never reaches you', and the required OS permission. The one gap is that the control-session framing is not reconciled with readOnlyHint=true, leaving mild ambiguity about whether the call itself only mints a link.

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 purpose is front-loaded in the first clause and each subsequent sentence adds non-redundant information (user capabilities, privacy, follow-up screenshot, platform/permission limits). The opening sentence is somewhat dense with its colon-list, but nothing is filler.

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, one fully documented parameter, and annotations carrying the safety profile, the description supplies everything else an agent needs: when to invoke, the hand-off mechanics, the follow-up action, and the environment prerequisites. It also makes clear the tool yields a link to be handed to the user.

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% for the single deviceId parameter, which already explains 'computer name or id from list_devices; optional with one computer'. The description only implies device targeting ('one of their computers') and adds no syntax or selection detail, so the schema does the heavy lifting – the baseline 3.

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 states a specific action on a specific resource – produce a live-control link for one of the user's computers – and even distinguishes the workflow from its sibling by telling the agent to 'take a screenshot to see where things stand' afterward. An agent can tell this apart from 'screenshot' 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?

It names concrete situations that select this tool ('to sign in, pass a CAPTCHA, approve a payment or anything else only they should do') and states the post-condition workflow: wait until the user reports they are done, then screenshot. Preconditions (works on Macs, needs Live screen permission owned by the machine's owner) are explicit.

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