DM someone who commented

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

Annotations already declare this as a non-read-only, non-idempotent, open-world mutation, so the safety profile is covered. The description adds genuinely non-obvious behavior beyond that: a hard one-message-per-comment limit, a 7-day eligibility window, and a mandatory user-confirmation step before sending. It does not describe what happens when the window has expired or when a duplicate is attempted, which is the remaining gap.

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?

Three short sentences, none wasted: purpose first, then constraints, then the confirmation prerequisite. The most important scoping rule (one message per comment) is front-loaded.

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 four-parameter mutation with no output schema, the description covers the essential decision inputs: recipient derivation, rate limit, time window, and the approval gate. Missing only edge-case behavior and error outcomes, which is a modest gap rather than a blocker for correct invocation.

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%, so the description must carry weight, and it does: it explains that the recipient is derived from the comment (clarifying comment_id's role beyond a bare string) and that confirmation must occur before the call, giving the confirmation_token lifecycle context the schema only hints at. The account parameter is left entirely to the schema, which does document it adequately.

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 states a specific verb and resource ("Send one private Direct message to the person who wrote a comment") and adds a concrete example of the intended content ("the link they asked for"). This clearly separates it from the public-facing reply_to_comment and the general send_dm siblings.

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 gives explicit qualifying conditions — one message per comment, within 7 days — and notes the user must confirm first, which tells the agent when this call is appropriate. It stops short of naming the sibling alternatives (reply_to_comment for public replies, send_dm for arbitrary recipients), leaving that routing implicit.

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