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

Annotations already cover safety (readOnly, idempotent, non-destructive, openWorld), yet the description adds real behavioral value: a cost disclosure ('5 points per returned record') and a depth limit on reply expansion ('up to 3 levels deep'). It still doesn't say how max_items interacts with replies or how results are paginated, so it falls short of a 5.

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?

A single tight sentence front-loads the resource, then lists returned fields, reply depth, and cost. No filler, no restatement of the title.

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 enumerates returned fields (text, date, author, likes, reply count), and the cost model is disclosed. Minor gaps remain around pagination and whether max_items caps top-level comments only, but nothing critical is missing for correct invocation.

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; the description goes beyond it by clarifying that include_replies expands to 3 levels and that each reply counts as a returned record for billing purposes. It adds no insight into sort modes or the newer_than date/period grammar.

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 action and resource (fetch comments from public Facebook posts/photos/videos/reels) plus the fields returned, which is enough to distinguish it from run_facebook_posts or run_facebook_reviews without opening a schema. It stops short of naming any sibling explicitly.

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 only implied: 'public Facebook posts' hints at the eligibility boundary, but there is no explicit when-to-use/when-not, no mention of how it differs from run_facebook_posts or run_facebook_reviews, and no note that non-public content is unsupported.

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