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

Annotations already declare readOnlyHint=true and destructiveHint=false, so safety is covered; the description adds value beyond that with per-page billing ('Billed $0.008 per page') and an explicit enumeration of returned fields (text, author, reaction/reply counts, date, attachments). It does not disclose pagination/cursor behavior.

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?

Three sentences, front-loaded with the core action and resource, followed by output contents and pricing. Every sentence earns its place with no filler.

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?

With no output schema, the description usefully summarizes the return fields, and it covers the ID source, pagination range, and cost. It is nearly complete; only cursor/pagination continuity and rate-limit behavior are left implicit.

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 are already documented in the schema. The description reinforces the pfbid-or-numeric format for post_id and ties billing to pages, but adds no syntax or meaning beyond what the schema already carries, making 3 the correct baseline.

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 ('Get the comments on a Facebook post by post ID') and immediately clarifies the ID format (pfbid or numeric). An agent can distinguish it from siblings like facebook_page_posts (the post source) or search_facebook_posts without opening a schema.

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?

Names the prerequisite workflow by pointing to facebook_page_posts, facebook_group_posts, or search_facebook_posts as sources of the required post_id, which tells the agent how to be in a position to call this tool. It stops short of stating when-not-to-use it or naming a comment-specific alternative.

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