ariel_reply

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

Annotations (readOnlyHint=false, destructiveHint=false) already establish this as a non-destructive write, lowering the bar. The description adds one genuinely useful behavioral trait beyond annotations: automatic thread-root resolution, which affects where the reply lands in the conversation tree. However, it does not disclose authentication requirements (relevant given the ariel_auth_status sibling) or failure/error behavior, and there is no output schema describing the response.

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?

Two short sentences with zero filler. The primary purpose is front-loaded in the first sentence, and the single most valuable behavioral detail (thread-root resolution) occupies the second. Every word 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 write operation, the description plus annotations cover purpose, safety profile, and the key threading behavior, and the schema fully documents parameters. The notable gap is the return value: there is no output schema and the description never states what the agent should expect back (e.g., the created reply's AT URI, which it would need for follow-up actions like like or delete). Authentication context is also absent.

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% — text, langs, and parentUri each carry descriptions in the schema, so the baseline is 3. The description adds only marginal value by connecting parentUri to the thread-root resolution behavior, but provides no parameter syntax or format detail beyond what the schema already states.

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 names a specific action ('Reply') and resource ('a post') in the opening sentence, making the core purpose unambiguous. The second sentence adds a distinguishing behavioral detail (automatic thread-root resolution). However, it never explicitly contrasts with sibling tools like ariel_create_post, ariel_quote_post, or ariel_create_thread, so differentiation rests entirely on the verb 'Reply' rather than named comparison.

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?

Usage context is implied by the verb: use this when the intent is to reply to an existing post. The thread-root resolution note implicitly argues for using this over manually constructing a reply, but the description gives no explicit when-to-use/when-not-to-use guidance and names no alternative tools, despite a large sibling set of overlapping post-creation actions.

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