list_audio_devices

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

With no annotations, the description carries the full burden and delivers: it discloses the platform backend (DirectShow), that results are machine-local, that one entry is flagged as a probable loopback, and that microphone devices are out of scope. It stops short of describing the returned structure (field names, how the flag appears), which is the only notable gap.

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?

Three sentences, front-loaded with the action, then the usage handoff, then the constraint. No redundant restatement of the name or title.

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 and no annotations, the description must supply all context, and it covers purpose, consumer, platform, and limitations. The return value shape — how the loopback flag is surfaced — is the one thing an agent must discover by calling, keeping this short of a 5.

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 takes zero parameters, so the baseline of 4 applies; there is nothing for the description to disambiguate beyond noting that no filters or selectors are accepted.

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?

States a specific verb and resource ('List the DirectShow audio devices ffmpeg can see on this machine') plus an extra behavior (flagging a likely loopback device). It is clearly distinguishable from siblings like start_recording, which consume rather than enumerate 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?

Explicitly instructs to 'Use the returned name as the `audio` device for start_recording', tying this enumeration tool to its consumer. It also states the exclusion — system audio requires Stereo Mix or a virtual-audio driver, and microphone capture is not supported — so the agent knows when this tool is applicable.

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