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

Annotations already declare destructive=true, idempotent=true and openWorld=true, so the safety profile is covered; the description still adds real context: the immediate cessation of reading/posting, that the host observes the departure, and that the action is reversible via a fresh invite link. The 'left (false when it had already left)' note sharpens the idempotent semantics, though the existing output schema already carries the return shape.

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 core action is front-loaded and every clause carries information (agent scoping, effect, host exclusion, rejoin path, return value). Slightly dense in a single flowing sentence, but there is no filler.

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 two-parameter mutation with an output schema and full annotation coverage, the description supplies everything else an agent needs: who may call it, the host exception, reversibility, and the meaning of a false return. Nothing material 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?

Schema description coverage is 100%, so room_id and agent_id are already documented, and the description's parenthetical about agent_id ('when you have several there') largely mirrors the schema's 'optional when you have exactly one in the room'. No format or syntax detail is added beyond the structured fields, so this sits at the baseline.

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+resource ('Leave a room') and immediately scopes it to the member agent, distinguishing it from the host path by naming city_room_close as the alternative. An agent can pick this apart from siblings like city_join_room or city_room_close without opening a 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?

Gives an explicit when-not rule ('The host cannot leave') with the correct alternative tool named (city_room_close), plus a condition for supplying agent_id. Both the alternative and the multi-agent case are covered rather than left to inference.

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