get_default_device

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

No annotations exist, so the description carries the full burden. It usefully discloses the resolution source (runtime override or the ADB_SERIAL variable), which is real behavioral context beyond the schema. However, it does not confirm side-effect-free semantics, describe failure behavior when nothing is set, or note any fallback ordering beyond the two named sources.

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?

A single sentence that front-loads the returned value and adds one clarifying clause. No filler, no restatement of the tool name.

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?

Zero parameters, an output schema that covers the return type, and a clear statement of what value is produced. For a trivial getter this is nearly complete; the only omission is what happens when no default is configured and how it relates to set_default_device.

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 tool takes zero parameters, so the schema has nothing to document and the baseline is 4. The description's mention of ADB_SERIAL usefully explains where the returned value originates rather than leaving the agent to guess.

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: returns the active default device serial. It distinguishes itself implicitly from the sibling set_default_device and from get_devices by naming the exact value returned. It does not explicitly contrast with those siblings, so it falls short of a 5.

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?

There is no when-to-use guidance and no routing to alternatives. With siblings like get_devices and set_default_device present, the agent gets no signal about when this narrow getter is preferable to enumerating devices or how the two relate. The parenthetical hints at resolution order but is not usage guidance.

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