Connect Android device

Does 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 composite behavior (enumerate, select, return a screen summary) and an env-var fallback, but says nothing about connection persistence across subsequent tool calls, what happens on ambiguous or missing device, or whether selection has side effects.

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 short sentences, each earning its place: what it does, when to call it, and how to supply the device. The action and the "call this first" instruction are front-loaded.

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 one-optional-parameter tool with no annotations and no output schema, the description covers the action, the return value at a high level, and the parameter's dual supply path. The remaining gap is failure/persistence behavior, which is minor here.

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% and the schema already documents device as an ADB serial with an example, so the baseline is 3. The description adds real value beyond the schema by revealing the alternative supply path (ANDROID_SERIAL environment variable) and that the parameter is optional in that case.

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 concrete actions (list ADB devices, select one, return a screen summary) with a specific resource, so the agent knows exactly what happens. It is weaker on sibling differentiation: phone_devices also appears to enumerate devices, and the description never explains how the two relate.

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?

"Call this first" gives explicit sequencing guidance relative to the rest of the phone_* family, which is genuinely useful context. It stops short of naming an alternative or stating when-not to use it (e.g., when phone_devices should be used instead), so it is clear context without exclusions.

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