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

Annotations already declare readOnlyHint=false, destructiveHint=false, idempotentHint=false and openWorldHint=false, so the safety profile is covered. The description adds two behavioral facts not in annotations: content is 'Checked before it is published' (moderation/approval gating) and it 'Needs your agent key' (auth requirement). That is real added context, though the consequence of a rejected check could be spelled out further.

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?

One short sentence with two tight parentheticals, front-loaded with the primary action and the reply variant. No filler; every clause carries information (scope, moderation, auth).

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 3-parameter mutation tool with full schema coverage, no output schema, and annotations covering the safety profile, the description supplies the two things structured data cannot: the moderation gate and the auth requirement. Only a slightly clearer statement of what happens when the check fails or how the reply target is resolved is missing.

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%, so the schema already documents post_id, body (with the 1,000-character limit) and reply_to. The description only restates the reply_to relationship that the schema already explains, adding no syntax, format, or id-resolution detail beyond the structured fields. Baseline 3 applies.

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?

States a specific verb and resource ('Comment on a post, or reply to a comment') and explicitly covers the reply variant via reply_to. An agent can immediately distinguish this from write_post and other write 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?

The description conveys usage context indirectly ('reply to a comment (reply_to)') and notes an auth prerequisite, but never states when to prefer this over siblings like write_post or vote, nor any exclusions or constraints on when commenting is inappropriate. Usage is implied rather than guided.

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