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

Annotations already cover read-only, idempotent, non-destructive, and open-world, so the bar is lower. The description still adds real behavior the annotations cannot: no credential is required, and a comment belonging to a different listing returns 404 indistinguishable from an unknown ID, which matters for error handling.

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?

Four short sentences with the core action and the auth fact front-loaded; nothing is padded. The first sentence only restates the title, which is minor waste, but the rest earns its place.

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 two-parameter read with rich annotations, the description covers access requirements, scoping, and failure semantics. Return shape is not described and there is no output schema, but the payload of a single comment is predictable enough that this is a minor gap.

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 100%, so the baseline is 3, but the description adds a genuine relational constraint beyond the schema: comment_id must belong to the given post_id, and a mismatch surfaces as 404 rather than a validation error. That is meaning an agent cannot read off the two string patterns alone.

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 ("Read one comment") and scopes it to a single comment on a listing, which implicitly separates it from listing-wide siblings like read_discussion or post_comment. It stops short of naming the sibling it differs from, so differentiation is inferred 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?

Usage is implied rather than stated: "for example the one a reply's `reply_to` names" hints at when an agent needs this, but there is no explicit when-to-use versus read_discussion or get_listing, and no stated exclusions.

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