Device info

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

readOnlyHint=true already tells the agent this is a safe read. The description adds nothing beyond that: it doesn't say whether it errors when multiple devices are online without a serial, whether an emulator qualifies, or how failures surface.

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 fields with zero filler. It is efficient, though it reads as a return-value list rather than a statement of purpose.

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 usefully enumerates what comes back, which is the main gap it needed to fill. Missing only edge-case behavior (multi-device ambiguity, offline devices), which the schema partially covers.

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 serial parameter is documented in-schema with its optionality rule. The description adds no meaning about the parameter, so the 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?

The description enumerates exactly what the tool reads (model, Android version, API level, ABI, screen size, density), which makes the resource unambiguous. It lacks an explicit verb and does not distinguish itself from siblings like devices_list or environment, so an agent must infer it is a metadata read, not a listing.

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?

No guidance on when to call this instead of devices_list or environment, and no stated preconditions such as a device being online. The only usage hint (serial optional when one device is online) lives in the schema, not the description.

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