List Devices

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

Annotations already declare readOnlyHint=true, so the read-only nature is covered. The description adds useful behavioral context beyond that: these devices are 'local devices already connected to this machine, ready to use immediately at no cost.' This informs the agent about the operational state and cost implications, which is not in the annotations.

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?

The description is concise yet comprehensive, front-loading the core purpose ('List all available devices') before elaborating on scope and the alternative. Every sentence adds value, and the structure is logical, making it easy for an agent to parse quickly.

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?

Given the tool has no parameters, no output schema, and readOnlyHint annotation, the description provides all necessary context: what devices are listed, their local nature, cost, and the alternative for remote devices. Nothing an agent needs to correctly invoke or interpret the result is missing.

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 input schema is fully covered (100% coverage trivially). The description does not need to elaborate on parameters, and with no parameters to describe, a baseline of 4 is appropriate per the scoring rules.

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 action ('List') and the resource ('all available devices'), and specifies the exact scope: physical devices, simulators/emulators, Android and iOS. It also explicitly contrasts with the remote fleet alternative, making the tool's purpose unambiguous and distinct from siblings.

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 provides explicit guidance on when to use this tool versus an alternative: 'for devices from the shared remote cloud fleet, use mobile_list_remote_devices instead.' This directly addresses selection between the two listing tools, which is the primary alternative.

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