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

Annotations already declare it is a non-read-only, non-idempotent action, and the description usefully adds that the character listens via microphone, speaks aloud, and the session lasts up to a minute. These are behavioral facts absent from the structured fields. It stops short of stating microphone-permission requirements or what happens when the minute expires.

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 short sentences, each earning its place: the action, the runtime behavior, and the argument source. No filler and the core action is front-loaded.

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?

An output schema exists, so return values need no explanation, and the description covers the interaction model (voice in, voice out, one-minute cap). It is nearly complete for a one-parameter tool, with only permission/blocking nuances left implicit.

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?

Only one parameter, and schema coverage is 100% with a full enum plus its own description. The text only points back to list_characters as the source, which the schema description already says verbatim. Baseline 3 applies since the schema does the heavy lifting.

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: 'Open a live voice conversation with one bitHuman house character.' This is clearly distinguishable from list_characters (enumeration) and make_character_video (video generation) without opening any schema.

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 tells the agent where to source the required argument: 'Use a character id from list_characters.' That is a real routing instruction to a sibling. It does not, however, say when NOT to use this tool or contrast it with make_character_video, so it falls short of full when/when-not guidance.

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