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

Goes well past the annotations: discloses the data source (facebook.com), that access is via a residential proxy, and a full pricing model — $0.01 USDC per successful call via x402 on Base/Solana/Arc, with failed calls free. Cost and payment mechanics are exactly the kind of context an agent needs before invoking a paid tool, and annotations only cover read-only/open-world.

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?

Two sentences, front-loaded with the resource and what it returns before the operational logistics. The pricing sentence is dense but every clause (price, currency, protocol, chains, failure policy) carries actionable information.

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 field-level return documentation is unnecessary. With source, access method, auth posture, and billing model all stated, an agent has everything required to decide and call 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?

Schema description coverage is 100% and already documents the single 'page' parameter with accepted formats (username, numeric id, URL). The description adds nothing further about the parameter, 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 specific verb+resource ('Contact details from a Facebook Page's About tab') and enumerates the returned fields (category, email, phone, website, address, social links, page name, followers). This clearly separates it from sibling list-oriented tools like social_facebook_pages or social_facebook_likes.

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 parenthetical '(logged-out view)' implies no authentication is needed and tells the agent which vantage point the data reflects, which is useful scoping. However, it never states when to pick this over social_facebook_pages or social_contact_info, nor any failure conditions or exclusions.

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