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

Annotations already mark the operation as non-read-only and destructive, so the safety profile is covered. The description adds the password condition but no additional behavioral context such as membership side effects or failure modes; still, it does not contradict the annotations.

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?

Two short sentences, front-loaded with the core action and follow-up with the conditional parameter rule. 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 low-complexity join operation with only two parameters and an output schema, the description plus annotations cover the essential conditions: what to supply, when the password is needed, and the operation's side-effect profile.

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 coverage is 100%, so invite_code and password are already documented. The description reinforces the password rule, but 'only if protected' largely restates the schema's own 'only required for password-protected rooms,' adding only marginal guidance.

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 clear action and target: 'Join a room using its invite code.' It names the mechanism (invite code) and implies an existing room, which separates it from create_room, but it does not explicitly distinguish itself from siblings such as get_room or list_rooms.

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?

Provides the central prerequisite (invite code) and an explicit conditional rule for when the password should be included ('only if the room is protected'). It does not name alternatives or state exclusions, but the join-vs-create context is clear enough for an agent to route correctly.

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