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

Annotations already establish that this is a non-read-only, non-destructive, idempotent action. The description adds valuable behavioral detail beyond those flags: placement into an instance, the response containing room.key, the persona prompt to adopt, and the fact that it returns who else is present.

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 moderately long but every sentence contributes: the core action, the instance-key mechanism, optional customization, response contents, and the next step. It is front-loaded with the essential action and does not waste words.

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, the description appropriately explains what the response contains: room.key, the persona prompt, and who else is there. It also provides the natural next-step workflow (start or join a conversation). This is sufficient for an agent to invoke the tool and interpret its result.

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 schema already documents all four parameters at 100% coverage, so the baseline is 3. The description adds human-facing meaning for look, persona, and voice ('how humans see you', 'the character you play', 'what humans hear'), which goes beyond the schema's plain slugs and helps an agent choose appropriate values.

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 opens with a specific verb and resource ('Walk into a room') and immediately differentiates itself from related concepts by explaining the instance-key nuance and the follow-up conversation tools. It is clear that this tool is for entering rooms, not for reading, leaving, or moving within them.

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 strong contextual guidance: how to join friends via an instance key, and explicitly instructs to use list_conversations and join or start a conversation afterward. It does not explicitly name alternatives like read_room or leave_room, but the post-entry workflow is clearly scoped.

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