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

Annotations only say readOnly and openWorld; the description adds substantial context beyond that — approximate result cardinality (~a dozen), people-only restriction, the fields returned, and the exact cost/auth model ($0.05 USDC per successful call via x402 on Base or Solana, or API key). The per-call charge is critical pre-invocation information an agent would otherwise miss.

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?

Three tight sentences: what it returns first, the follow-up tool second, cost/auth last. Zero filler and every clause carries information an agent needs before selecting or calling the tool.

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?

There is no output schema, yet the description enumerates the returned fields (name, numeric profile ID, profile link, public details), the result volume, and the payment/auth path. Nothing material is missing for a single-parameter lookup.

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?

Only one parameter and schema coverage is 100%, so the schema alone documents 'name' with an example ('John Smith'). The description reinforces that it is a person's name rather than a username or ID, but adds no format or matching-rule detail (e.g. exact vs fuzzy) beyond the schema. 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 (people search by name) with scope qualifiers: Facebook's public directory, ~a dozen results per name, people only. It also distinguishes itself from the sibling facebook_profile by explaining that the latter takes an ID for the full profile.

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?

Explicitly routes the agent: use this to find candidates by name, then 'Pass an ID to facebook_profile for the full public profile.' That names the alternative sibling and the condition that selects it, so no inference is required.

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