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

Annotations already declare this is read-only, idempotent, and non-destructive, so the description's safety burden is low. It adds useful behavioral context by specifying that the response includes members and quick actions, which is beyond what the input schema provides. It does not contradict any annotation.

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 a single, efficient sentence that front-loads the core operation and then adds the relevant scope of returned data. Every word earns its place; there is no redundancy or 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 simple read-only lookup with one fully documented parameter, an output schema, and safety annotations, the description provides everything an agent needs to invoke the tool correctly. No missing prerequisites, side effects, or return-format details are required for this level of complexity.

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 single parameter 'invite_code' is already fully documented in the schema as 'Room invite code.' The description echoes that it fetches by invite code but adds no extra semantic detail such as format, length, or example values. Baseline 3 is appropriate because schema coverage is 100%.

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 uses a specific verb ('Fetch'), names the resource ('a single room'), and identifies the exact lookup key ('invite code'). It also clarifies scope ('single room') and includes expected contents ('including members and quick actions'), making it clearly distinct from sibling tools like list_rooms and create_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 implies this tool is for retrieving one specific room rather than listing all rooms, but it does not explicitly state when to prefer it over alternatives such as list_rooms or get_live_status. The intended use is reasonably inferable, but no explicit routing guidance is provided.

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