list_phones

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

The description discloses that the tool reports reachability, which is a behavioral trait. However, with no annotations provided, the description carries the full burden. It doesn't mention whether the tool performs any network checks, caches results, or has side effects, but for a simple listing tool this is acceptable. The reachability disclosure adds value beyond the schema.

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?

Two sentences, no wasted words. The first sentence states the core function and output. The second sentence provides essential cross-tool context. Information is front-loaded and every sentence earns its place.

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 zero-parameter listing tool with an output schema, the description is complete. It explains what the tool does, what the output means (reachability), and how the results are used by other tools. No critical information is missing for an agent to call it correctly.

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 has zero parameters, so the schema is trivially complete. The description adds context about how the output relates to other tools (the `device` parameter used elsewhere), which is valuable. Baseline for 0 params is 4, and the description earns it by explaining the significance of the listed phones.

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 clearly states the tool's function: listing phones the server can drive and their reachability status. It distinguishes itself from sibling tools like list_devices and list_adb_devices by focusing on phones the server can drive, not generic devices or ADB devices.

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?

The description explicitly explains when to use this tool: to see available phones, and it provides critical guidance that every other tool takes an optional `device` parameter naming one of these phones. It also instructs the agent to always name the device when multiple phones are configured, which is essential for correct usage.

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