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 proactively discloses that the handler reconstructs the target from the parent, that a resolved parent is re-opened, and that nested replies flatten to single depth causing reply-to-reply to re-point to the root. These are non-obvious behaviors well beyond what the schema conveys.

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 long, front-loaded with the tool's purpose, and every sentence adds unique value: what it does, why it's convenient, and key behavioral subtleties. There is no filler or redundancy.

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 3-parameter tool with no output schema, the description is fully adequate. It covers the tool's purpose, parameters, threading behavior, and side effects (re-opening resolved parents). There are no obvious gaps that would hinder the agent from invoking it correctly.

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?

The schema already provides 100% coverage for all three parameters, including clear descriptions for comment_id and body. The description adds a small amount of context about parent reconstruction and mentions the same validation/fan-out rules for mentions, but it doesn't substantially extend parameter semantics beyond the schema. Baseline 3 is appropriate.

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 clearly states it is a 'Convenience wrapper around `add_comment` for the common reply case,' specifying the exact verb (reply) and resource (comment). It distinguishes itself from the sibling add_comment by framing it as a reply-specific wrapper, and the parameter mention (parent comment id and body) makes the operation unmistakable.

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 explicitly positions the tool for the 'common reply case' and explains the benefit: the agent doesn't need to know the parent type. It also references 'Same threading rules as add_comment,' tying it to its sibling. However, it doesn't explicitly state when NOT to use it (e.g., for direct add_comment calls), though this is implied by 'reply case.'

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