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

Annotations already cover read-only/mutation, idempotency, and destructiveness. The description adds useful behavioral context beyond those: an invitation is a prerequisite, and the room must be in invite-mode. This is valuable operational guidance that annotations do not express.

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 two tightly written sentences with no filler. The core usage comes first, and the exception (token-mode rooms) is parenthetical, making the instruction easy 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?

For a single-parameter, no-output-schema tool, the description supplies the essential context: when to join, what kind of room, and the prerequisite of being invited. Annotations cover side effects and idempotency, so nothing needed for correct invocation 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 schema only says room_id is a UUID with no description, and the description never explicitly defines the parameter. Still, the phrase 'a Parlor you were invited to' implies room_id identifies that invited Parlor, so the description adds minimal contextual meaning beyond the schema. With 0% schema coverage, it does not fully compensate, but the single self-explanatory parameter keeps this at an adequate level.

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 a specific action ('Join an invite-mode Parlor') and the resource affected, while distinguishing it from token-mode rooms. It also differentiates this tool from siblings like continental_room_open or continental_room_invite by specifying the exact invitation context.

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 explicitly says when to use this tool (when invited to an invite-mode Parlor) and when not to use it (token-mode rooms need no join; present the token instead). This gives the agent a clear decision rule without needing to inspect other tools.

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