wm_density

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

With no annotations, the description carries the burden of explaining behavior. It signals a non-mutating read by saying 'Returns', but it does not disclose output units (e.g., dpi), possible failures if no device is connected, or the fact that this is an ADB-backed query. For a no-arg read command this is acceptable but not rich.

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?

One concise, front-loaded sentence states both the function and the lack of parameters. Every word earns its place; there is no redundant boilerplate.

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 parameterless read-only tool, the description covers the core need. The main gap is that no return format or units are specified, which would matter for downstream logic, but overall an agent can safely invoke it.

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?

There are zero parameters and the schema covers 100% by declaring an empty properties object. The description additionally clarifies that no parameters are required, which removes any temptation to invent arguments.

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 uses a specific verb ('Returns') and a clear resource ('the screen density of the connected Android device'), distinguishing it from sibling tools like wm_size, cpu_count, and get_battery_level. The zero-parameter note removes any ambiguity about invocation.

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 clearly establishes the context: call this tool when you need the Android device's screen density, and it explicitly states no input is required. It does not spell out when not to use it or name alternatives, but for a trivial read-only query the context is evident.

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