join_room

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

With no annotations provided, the description fully discloses the mutating behavior, failure conditions (room full, doesn't exist, already in room), and return values (room_id and slot). There is no contradiction with structured fields.

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 concise, front-loaded with 'Mutating', and each sentence serves a specific purpose: precondition, parameter source, return, failure cases, and next steps. No extraneous information.

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?

Given no annotations, no output schema, and 2 parameters, the description covers most essential behavioral details. The only gap is the lack of explanation for connection_id, but overall it provides enough context for correct tool invocation.

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 input schema has 2 parameters with 0% schema coverage. The description explains room_id as 'the room's string identifier from list_rooms' but does not explain connection_id, leaving the agent to infer its purpose. This partially adds value over the schema.

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 explicitly states 'Join an existing room' using a specific verb and resource. It distinguishes from sibling tools like 'create_room', 'leave_room', and 'list_rooms' by providing context about the room lifecycle and preconditions.

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 clearly specifies when to use this tool: requires state=in_lobby and set_player_metadata first. It also gives explicit guidance on next steps (call set_ready) and alternatives for leaving (use leave_room).

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