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

Annotations already declare readOnly/idempotent/non-destructive, so the bar is lower. The description still adds real value beyond structured fields: a prompt-injection warning that messages are untrusted_peer_content to be treated as data, plus 'Empty is allowed' and reinforcing read-only behavior. 'No proof' is terse but consistent with the schema's proof params.

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?

Front-loaded with purpose and mode, then security guidance, then the alternative routing. Sentences are short and mostly earn their place, though terse phrases like 'Empty is allowed' and 'no proof' assume context.

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?

With an output schema present, return values need not be explained, and the description covers purpose, mode, routing, and the untrusted-content handling. Auth parameters are fully covered by the schema, so the definition is complete enough to invoke correctly.

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 all five parameters including auth mechanics are already documented in the schema. The description only restates the id behavior ('omit to list all rooms'), adding no semantics beyond what the schema provides. Baseline 3 is correct.

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 specific verb (Reads) and resource (group rooms), and distinguishes two modes: list all rooms vs. one room with its messages via id. It even names the sibling (plaza_list) for the public-board case, so an agent can differentiate without opening schemas.

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?

Explicitly routes the agent: pass id to get a single room with messages, and 'For the public board use plaza_list' names the alternative for a different use case. The mode-selection condition is stated rather than left to inference.

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