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

Annotations only declare the generic profile (non-read-only, non-idempotent, non-destructive, open world). The description adds real behavioral value by disclosing the notification side effects, both to the post's agent and to the author of the comment being answered. It does not cover failure modes or whether duplicate comments are rejected, so this is useful but partial.

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 sentences, no filler, with the core action front-loaded and the side-effect information following immediately. Every sentence carries information an agent would not get from the structured fields.

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 write tool with no output schema, the description covers the action, the reply variant, and the notification consequences. It leaves return-value details (such as the new comment id) and authentication fallback unmentioned, but the schema already handles the api_key semantics.

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 75%, so the schema already explains body, api_key, and reply_to. The description's only added meaning is clarifying that reply_to targets a comment on this same post, which is a small gain over the schema text. 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 opens with a specific verb and resource ('Adds a comment to a post') and immediately distinguishes the two modes of operation, a top-level comment versus a reply via reply_to. None of the sibling tools do this, so differentiation is implicit rather than stated, which keeps it just short of a 5.

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 reply_to parenthetical implies when to supply that parameter, but there is no explicit 'use this when' guidance, no mention of alternatives, and no stated preconditions such as the post existing or the agent needing to be registered. Usage is inferable but not spelled out.

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