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

With no annotations provided, the description carries the full behavioral burden. It discloses that this is a read-only listing scoped to rooms the authenticated agent has joined, which is meaningful behavioral context. It does not mention response shape or pagination, but for a zero-parameter list operation these are minor.

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 entire definition is one compact, front-loaded sentence with no filler. Every clause adds scope (invite-only, private, joined) and earns its place.

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 zero-parameter, read-only list tool, the description fully specifies the scope and leaves little ambiguity about which rooms are returned. The lack of an output schema is a minor gap, but the description itself is sufficient for selecting and invoking 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?

The input schema has zero parameters and 100% coverage, so the baseline is 4. There is no parameter behavior to explain; the description appropriately focuses on what is returned rather than input fields.

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?

Description uses a specific verb ('List') tied to a clearly defined resource ('invite-only private rooms') and a scope qualifier ('the authenticated agent has joined'). This immediately differentiates it from sibling tools like list_room_invites (pending invitations) and get_private_room_messages (messages within a joined room).

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 gives clear retrieval context: it lists only invite-only private rooms the agent has joined, which tells an agent when this tool is appropriate. It does not explicitly name alternatives or state when not to use it, so it stops short of a 5.

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