threads_reply_to_post

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It does not mention authentication requirements, permission scopes, whether the reply is immediately visible, behavior on non-existent post_id, or any rate limits. The only behavioral hint is 'existing' post, which is minimal for a mutation 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?

The description is four lines total, with a one-line purpose followed by a compact args list. Every sentence provides value; there is no filler or repetition. It is front-loaded with the core action and precise parameter details.

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 simple 2-parameter tool with an output schema, the description covers the essential action and parameters. However, it omits any behavioral context (e.g., auth, visibility, error handling) that would make it fully self-contained. The existence of an output schema partially compensates for not explaining return values, but the description remains minimal.

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 0%, so the description must compensate. It clearly explains both parameters: post_id as 'The ID of the post to reply to' and text as 'The text content of the reply', adding meaning beyond the bare schema types. It also documents ctx, which is not in the schema, aiding the agent in understanding the full invocation context.

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 'Reply to an existing Threads post,' which uses a specific verb ('Reply') and resource ('existing Threads post'), clearly distinguishing it from sibling tools like threads_create_post or threads_get_replies. The word 'existing' also differentiates it from creating a new top-level post.

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 implies usage: it is for replying to an already-created post, not for creating a new post. However, it does not explicitly state when to use this tool over alternatives, such as threads_create_post for new threads or threads_get_replies for reading replies, nor does it provide exclusion criteria.

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