既定デバイスを設定

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

No annotations are provided, so the description carries the full burden of disclosing behavior. It only says 'sets' a default, implying a mutation, but it does not reveal whether the change is persistent, whether the device must be already known/paired, or any side effects. This lack of behavioral detail is a significant gap for a state-changing tool.

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 a single, compact sentence that states the purpose without any redundant information. Every word contributes to understanding the tool, making it highly efficient.

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 simple setter with one parameter and no output schema, the description provides the core purpose. However, with no annotations, it omits important operational context such as prerequisites (e.g., device must be discovered), persistence of the setting, or error behavior, leaving some gaps for an agent to infer.

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 input schema has 100% description coverage (the 'name' parameter is described as 'デバイス名'). The description adds the contextual meaning of this being the default for omitted parameters, but it does not add substantial detail beyond what the schema already states. Baseline 3 is appropriate.

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: setting the device to be used when the 'device' parameter is omitted. It uses a specific verb ('set') and resource ('default device'), and the scope is distinct from sibling tools like list_devices, pair_device, or remove_device, making it easily distinguishable.

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 gives clear context: it is for configuring the fallback device when the 'device' parameter is not supplied. However, it does not explicitly exclude alternative tools or mention when not to use it, so it stops short of a full 5.

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