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

Beyond the readOnlyHint=false annotation, it discloses a concrete failure mode: 'persist_failed' means nothing is posted and the post cooldown does not start, plus it references a post cooldown mechanism. This is meaningful behavioral context, though it omits auth requirements and rate-limit specifics.

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 lead is front-loaded, but the parenthetical 'Creates a new discussion thread' merely restates the opening, and the full category enumeration duplicates the schema enum, so not every sentence 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 create tool with no output schema, the description covers the essential failure behavior and category defaults. It is largely complete, with the only real gap being prerequisites such as authentication, which the session_id parameter implies.

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 description coverage is 100%, so the schema already documents title, content, category, and session_id in full, including the same enum options. The description repeats the category values and default without adding syntax or meaning beyond the schema, matching the baseline of 3.

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 states a specific verb+resource ('Create a new forum thread') that is unambiguous and clearly distinct from the reply/edit/list siblings. However, it never names or contrasts an alternative sibling, so it stops short of the explicit differentiation a 5 requires.

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 never says when to use this tool versus alternatives such as forum_reply, forum_edit_thread, or forum_list. The category list and default hint at scope but provide no selection guidance, so the agent must infer usage entirely.

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