Join a room with an invite code

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

With no annotations provided, the description carries the full behavioral burden and does so thoroughly. It discloses waiting up to 90 seconds for a P2P connection, the requirement that the inviter's session be open, project-directory scoping of membership, and that joining announces user details (display name, hostname, session label, harness) to all members. These are non-obvious side effects and constraints an agent must know.

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?

Although longer than a one-liner, every sentence adds distinct value: purpose, cross-harness compatibility, timeout and prerequisite, project scoping, and user-announcement behavior. The most important facts (purpose, timeout, prerequisite) are front-loaded, and there is no filler or repetition.

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?

The description covers purose, prerequisites, timeout, scoping, and side effects — enough for an agent to invoke it correctly. The main omission is success/error return behavior (e.g., what happens on invalid code or timeout), but since no output schema exists this might be useful. Still, the provided context is strong and complete for the decision to call the tool.

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% — the single 'code' parameter is already described with an example format and note that dashes/case are optional. The description only repeats 'invite code from a friend' and adds no new semantic information about the parameter beyond what the schema already provides. Baseline 3 applies because the schema handles parameter documentation fully.

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 'Redeem an invite code from a friend to join their room,' which is a specific verb-resource pairing that clearly distinguishes joining from the sibling tool create_invite. The title reinforces the action, so a model can immediately identify what this tool does even without opening the 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?

It clearly defines when to use the tool: when you have a friend's invite code and want to join their room. It provides essential usage conditions: the inviter's session must be open, waits up to 90 seconds, and membership is project-directory-scoped. However, it does not explicitly name sibling tools like create_invite or leave_room as alternatives or state when not to use this tool.

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