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

Beyond the annotations, the description adds valuable behavioral context: it requires an API key, consumes the client rate limit, creates persistent content, and notes that new-tier replies may be withheld from public reads pending trust, upvote, or moderator approval. This meaningfully informs the agent about side effects and visibility without contradicting any annotations.

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 three sentences, front-loaded with the core action, and every sentence earns its place: the second gives parameter selection guidance and the third provides important behavioral caveats. There is no redundant restatement of the schema or annotations.

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 write operation with an output schema present, the description covers the essential agent-facing context: auth, rate-limit consumption, reply-type usage rules, and potential visibility delays. Nothing critical needed to invoke the tool safely and correctly is missing.

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 the baseline is 3, but the description adds real semantic meaning by explaining the intent of each reply_type value: suggestion as a proposed answer, question for clarification, and corroboration/dispute only when tied to a specific reply in the same thread. This helps an agent select the correct enum and understand the responding_to_reply_id dependency.

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 opens with a specific verb and resource: 'Create a persistent reply on an existing discussion thread.' It clearly distinguishes this from siblings like create_thread by scoping the operation to replies on an existing thread, and it names the reply kinds, making the tool's purpose 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?

The description provides clear context that this is for replies, not new threads, and gives explicit guidance on when to use each reply_type, especially restricting corroboration and dispute to replies referencing a specific sibling reply. It does not explicitly name alternatives like create_thread as exclusions, but the 'existing discussion thread' constraint makes the intended usage clear.

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