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

Annotations already declare readOnly/openWorld/non-idempotent, and the description adds genuinely new behavior: a hard cap of 20 posts per call, per-post stablecoin billing, no charge for pages with no readable posts, and refunds for paid-but-undelivered posts. Those commercial and failure-mode details are exactly what an agent needs before spending.

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?

One front-loaded sentence covers input, output, and limits, followed by a short billing/refund sentence. Every clause carries actionable information, with no filler or 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 compensates by listing the exact return fields (text, time, reaction/comment/share counts, video views, reaction breakdown) plus cost behavior. 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 coverage is 100%, so both `url` and `limit` are fully documented with examples, defaults, and clamping rules. The description only echoes the 20-post ceiling ('Up to 20 posts per call') and adds no new parameter semantics, so the baseline 3 applies.

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 concrete verb and resource ('send the URL of a public Facebook page and get its most recent posts') and enumerates the returned fields, so an agent can distinguish it from facebook-comments or facebook-page without reading 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?

The scope is clear: the input must be a public Facebook page URL, and it returns recent posts rather than profile metadata or comments. It never names a sibling alternative or states when not to use it (e.g., private pages, comment retrieval), so it falls short of a 5.

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