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

Annotations already establish the safe-read profile, yet the description adds substantial operational context: the $0.08 USDC x402 price on Base, the charge-only-on-success rule, the fact that this call returns payment instructions for a separate POST /v1/email, and the caveat that 'valid' means server acceptance, not human readership. This is exactly the behavioral detail annotations cannot carry.

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?

A single dense passage that front-loads the core action before moving to output shape, pricing, and caveats. Nearly every clause earns its place, though the return-field enumeration is partly redundant with the output schema.

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 paid, read-only lookup with an output schema present, the description covers purpose, cost model, payment flow, and verification semantics. It omits any account/credential prerequisites for the x402 payment flow, but is otherwise sufficient for an agent to invoke it 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%, so the baseline is 3. The description adds the found_only semantic (public-only, no pattern inference) and explains the meaning of the returned verification statuses, but contributes little beyond the schema for first_name/last_name/full_name.

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 and resource: 'Find one person's work email at a company domain.' The phrase 'one person's' implicitly contrasts with the batch sibling find_emails_batch, but nothing distinguishes it from basic_lookup or enriched_lookup, which the agent must resolve on its own.

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?

No guidance on when to choose this over basic_lookup, enriched_lookup, or find_emails_batch. The found_only parameter's effect is described, and the pricing/trial condition is stated, but neither tells the agent which sibling tool fits a given request.

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