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

Goes well beyond the readOnlyHint/openWorldHint annotations: discloses the approximate result count, that image URLs are signed and expire, the residential-proxy sourcing, per-call pricing ($0.01 USDC via x402) and that failed calls are free.

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?

Front-loaded with what the tool returns, followed by operational caveats. Dense but nearly every clause carries actionable information; the payment sentence is long but relevant to invocation cost.

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?

An output schema exists so return shape needn't be spelled out, yet the description still summarizes it and covers result count, URL expiry, sourcing and billing — everything needed to decide and invoke correctly.

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?

The single 'page' parameter has full schema description coverage (username, numeric id or Page URL), and the description adds nothing further about it — appropriate baseline since the schema does the work.

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+resource ('Latest photos on a Facebook Page's Photos tab') and enumerates the returned fields, which cleanly separates it from siblings like social_facebook_posts and social_facebook_reels.

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 'Photos tab' framing implies when this is the right tool over posts/reels, and 'logged-out view, usually 8' sets expectations, but no sibling is named and no explicit when-not guidance is given.

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