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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), so the description earns credit for the extra context: it restricts scope to public pages, specifies that a transcript is opt-in, and discloses the '5 points per returned record' cost — a genuinely useful trait for budget-aware agents. It does not mention pagination or rate limits.

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 front-loaded sentence with no filler; the two operating modes come first and the field list follows. The enumeration of returned fields is long but justified since there is no output schema; the trailing pricing note is compact and useful.

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 compensates by listing the returned fields, and it adds the public-page limitation and per-record cost. It leaves minor gaps (default of 20 items, pagination behavior), but nothing an agent needs to invoke it correctly is missing.

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 url, max_items, newer_than/older_than and include_video_transcript are already documented with examples and defaults. The description only echoes the video transcript option and the URL-based mode, adding no syntax or behavioral detail beyond the schema — 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 description uses a specific verb+resource ('Posts of public Facebook pages, or single posts by URL') and enumerates the fields returned, so an agent can immediately tell this is the post-extraction tool rather than a page lookup. It stops short of naming how it differs from siblings like run_facebook_search or run_facebook_comments, which share the same domain.

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 two modes given ('page or single post by URL'), which is a useful routing hint for the required url parameter. There is no explicit statement of when to prefer this over run_facebook_search or run_facebook_comments, and no exclusions or prerequisites beyond 'public pages'.

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