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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the description does not need to restate safety properties. The description adds a useful behavioral note about pagination ('use cursor when paginated'), which goes beyond the annotations. It does not describe rate limits, auth, or error behavior, but with annotations covering the read-only aspect, the added pagination detail justifies a mid-range score.

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?

The description is two short sentences, front-loaded with the core purpose ('List comments...') followed by a concise output/pagination note. There is no fluff or repetition. It is efficient and well-structured, though it could arguably be even more direct about the output format, but it earns a high score for being appropriately concise.

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?

The description covers the main action and pagination but leaves a notable gap: it says 'by URL' implying the url parameter is required, yet the input schema lists no required parameters. This could mislead an agent into thinking url is mandatory when it is technically optional (or the schema is an oversight). It also does not mention the optional feedbackId parameter, though the schema covers it. Given the tool's simplicity and comprehensive schema, the description is mostly complete but has this ambiguity.

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%, and the schema already documents each parameter (url, cursor, feedbackId) with clear descriptions. The description's mention of 'by URL' and 'use cursor when paginated' reinforces but does not add new meaning beyond the schema. Since the schema fully covers parameter semantics, a baseline of 3 is appropriate; the description adds minimal extra value.

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 clearly states the verb (list), the resource (comments on a Facebook post or Reel), and the method (by URL). This distinguishes it from a generic list tool, though it does not explicitly differentiate from the sibling facebook_post_comments_replies_list, which is for comment replies. The 'by URL' qualifier adds precision. It is not a tautology and provides a specific, actionable purpose.

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 provides no explicit guidance on when to use this tool versus alternatives. It mentions pagination ('use cursor when paginated') but does not note that for comment replies one should use facebook_post_comments_replies_list, nor does it clarify when to use this over facebook_post_get or other list tools. The usage context is implied from the name, but no explicit when-to-use/when-not-to-use instructions are given.

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