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

Annotations already declare the write profile (readOnlyHint=false, destructiveHint=false, openWorldHint=true), so the description's added value is the platform constraint on the target comment and the confirmation gate ("The user confirms first"), which explains why confirmation_token exists and that a prior identical call is expected. It omits failure modes beyond the top-level/hidden restriction and says nothing about rate limits or what a successful response contains.

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 compact sentences with the core action and its hard constraint front-loaded. "The user confirms first" is terse to the point of being slightly elliptical — an agent must connect it to the confirmation_token parameter — but no sentence is wasted.

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 4-parameter mutation with no output schema, the definition covers the main eligibility constraint and the confirmation workflow, which is the essential part. It still leaves the agent guessing about the returned value (the created reply's ID?) and about what happens if the target turns out to be a reply, which a write tool with no output schema arguably should state.

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 50% — only account and confirmation_token are documented inline, while comment_id and message have no schema descriptions. The description partially compensates by constraining comment_id to top-level, non-hidden comments, and the confirmation sentence implies how confirmation_token is used, but it adds nothing about message content or the account parameter. Baseline 3 reflects real but partial compensation.

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?

"Public reply under a top-level comment" gives a specific verb (reply) and resource (comment) plus a visibility modifier (public) that implicitly separates it from private_reply and comment_on_media. It stops short of naming those siblings, so the differentiation is inferable rather than explicit.

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 states clear exclusions — Meta does not allow replying to replies or hidden comments — which tells the agent when this call will fail and therefore when not to attempt it. It does not name competing tools (private_reply, send_dm, comment_on_media) for the cases this tool can't serve, so the agent must infer the alternative.

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