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

With no annotations, the description carries full behavioral burden. It discloses the endpoint type, server-side execution, the fact that Facebook blocks datacenter IPs, the "needs_proxy" status, and the proxy remedy. This is substantive transparency, though it does not specify the full set of possible statuses or response shape.

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?

The content is front-loaded and well organized in English, but the entire description is repeated verbatim in Vietnamese, doubling the length without adding new information for an AI agent. This redundancy wastes space and reduces conciseness.

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?

Given there is no output schema and no annotations, the description should explain what the tool returns. It mentions the "needs_proxy" status but does not specify the live/dead status format or any error cases. The core usage and proxy workaround are covered, so it is adequate but incomplete.

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 enriches the parameter meaning by emphasizing that the UID is numeric, clarifying the proxy format, and noting that the proxy is personal, per-request, and never shared — details beyond the structured schema.

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 clearly states the action (Check whether a Facebook UID is live or dead), the resource (a numeric Facebook UID), and the method (public profile-picture endpoint, server-side). It is specific and unambiguous, but it does not explicitly differentiate from the sibling check_health_bulk, so it falls short of a 5.

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 description gives practical guidance on the proxy fallback: if the tool returns "needs_proxy", the caller should pass their own proxy. However, it does not explain when to choose this tool over alternatives like check_health_bulk, so the vs-alternatives aspect is missing.

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