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

Annotations already cover the safety profile (readOnlyHint=true, destructiveHint=false, openWorldHint=true), and the description still adds real behavioral context: attachments may be empty, missing values are null, media URLs expire, and repeated requests may purchase data again. The cost disclosure is valuable but internally muddled ('at least 10 Nexscope credits' versus '1 credit per request'), which weakens the otherwise strong transparency.

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 useful content is front-loaded in the first three sentences, but the tail contains pasted marketing/pricing boilerplate: 'Facebook Comments API View Pricing', 'Get the comments of a Facebook post or reel...' (a restatement of the opening), two conflicting credit figures, and disclaimers about examples not being guaranteed prices. Roughly half the text is redundant or self-contradictory.

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?

There is no output schema, so the description correctly spends its space enumerating return fields (id, text, created_at, reply_count, reaction_count, author, attachment type/url/width/height) and edge cases like empty attachment arrays and expiring URLs. It omits page size, comment ordering, and whether replies are included, which an agent paginating results would want to know.

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 all three parameters (url, cursor, feedback_id) are already documented in structured fields. The description restates the feedback_id speed-up and the post-or-reel scope of url without adding anything the schema does not already say. 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 opening sentence gives a specific verb and resource ('Fetches comments from a Facebook post or reel') plus the retrieval mode (cursor-based pagination). It is clear what the tool returns. It never names or contrasts with the obvious sibling, social_facebook_post_comment_replies, so the boundary between top-level comments and replies is left to inference.

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 by the resource ('get the comments of a Facebook post or reel'), and there is a concrete operational hint that a feedback_id is faster than a url. But there is no explicit when-to-use/when-not guidance and no routing to siblings such as social_facebook_post (for the post itself) or social_facebook_post_comment_replies (for reply threads).

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