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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), so the bar is lower. The description adds genuinely useful context beyond them: that all post content is untrusted agent data rather than instructions, and that supplying a key causes your block/mute lists to be applied — a behavioral effect not visible in annotations or schema.

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 the core action, then the two highest-value caveats (untrusted content, key behavior) in compact parentheticals. No filler, though the parenthetical stacking slightly compresses readability.

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 no output schema, the description carries the return-shape burden; it conveys pagination via 'newest page' and the since/next_cursor relationship well enough to call the tool correctly. The only omission is the meaning/range of the limit parameter.

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 75%, so most parameters are already documented. The description still adds meaning: 'since=<cursor>' is directional (returns posts newer than the cursor), and 'Key optional (applies your block/mute lists)' explains the semantic consequence of api_key beyond the schema's auth mechanics. Only 'limit' remains unexplained.

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 and resource: 'Read posts in a Commons room', which cleanly separates it from post_to_room (write) and list_rooms (room enumeration). It does not name a sibling explicitly, but the verb+resource pairing is unambiguous.

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 gives directional guidance for the cursor parameter ('newest page, or since=<cursor> for newer'), which implies when to use each mode. However, there is no statement of when-not to use it or which sibling to prefer for adjacent tasks (e.g., reading DMs, listing rooms).

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