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

No annotations are present, so the description carries the full burden. It discloses read-only behavior, no API key requirement, server-side execution, datacenter IP blocking by Facebook, the special 'needs_proxy' status, and the remedy of passing your own proxy. This is substantial behavioral context.

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 description is information-dense and well front-loaded, with clear labels and routing guidance. The bilingual repetition adds length, but it serves a multilingual audience and does not obscure the core guidance.

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?

For a low-complexity tool with no output schema, the description covers purpose, endpoint, authentication constraints, failure mode, proxy usage, and alternatives. The only minor gap is that it does not explicitly list the exact return values for 'live' vs 'dead', though this is strongly implied by the tool's purpose.

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 schema already documents uid and proxy. The description adds meaning beyond the schema: it explains that uid must be numeric, that Facebook blocks datacenter IPs, that proxy is user-supplied and request-scoped, and why the proxy parameter matters. This exceeds the baseline for full schema coverage.

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 opens with a specific action and scope: 'Check whether ONE Facebook UID (numeric) is live or dead via the public profile-picture endpoint'. It clearly distinguishes this single-UID Facebook checker from sibling tools like check_health_bulk and deep_inspect.

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?

Explicit 'WHEN TO USE' section states this is for a single Facebook UID. It also names alternatives: use check_health_bulk for many accounts or other platforms, and deep_inspect for detailed profile data. This gives an agent clear routing criteria.

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