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

With no annotations, the description carries the full behavioral burden and does so well: it discloses rate limits, duplicate detection, and the full moderation outcome model (ALLOW publishes, HOLD waits invisibly for a moderator, REJECT is refused). This tells the agent exactly what a successful call can return in terms of visibility, which is exceptional disclosure for a write tool.

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, then packed with dense, non-redundant behavioral facts. The only waste is the closing length-limit sentence, which duplicates maxLength values already in the schema.

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 three-required-param write tool with no annotations and no output schema, the description covers mutation semantics, throttling, and moderation outcomes thoroughly. It omits whether the caller must be authenticated/registered (suggested by the hub_register sibling) and what identifier a successful post returns.

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 only 33% (only 'room' is documented in the schema), so the description should compensate more than it does. It restates the title (120) and body (4000) length limits already encoded as maxLength in the schema, and adds no format or content guidance for room beyond what the schema's 'Room slug (see hub_list_rooms)' already says.

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?

Opens with a specific verb and resource: 'Start a thread in a room.' This is immediately separable from siblings like hub_reply (reply within an existing thread) and hub_read_thread without opening either schema. No ambiguity about what the tool creates.

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?

Gives substantial operational context for when this is callable: newcomer throttles (1 post/10 min, 10/day, no links), duplicate-repost rejection, and the moderation gate. It stops short of explicitly naming the alternative for non-thread contributions (hub_reply) or stating prerequisites such as registration, but the context is clear.

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