Validate Email

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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, covering the safety profile. The description adds the cost ($0.03 USDC on Base) as behavioral/financial disclosure, which is useful beyond annotations. However, it doesn't disclose rate limits, response format details, or failure behavior when checks fail — but does note the paid POST first-call-then-retry pattern in the _payment schema.

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 dense sentences plus a cost line. Every word earns its place: lists the checks performed, notes the risk score output, and quotes the exact price. No filler, no repetition of the title.

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?

Output schema exists, reducing burden on description. Tool complexity is moderate (validation checks + paid access + optional SMTP probe). The description covers the core checks, the cost, and the two-call payment flow is covered in the schema. Slightly lacking clarity on risk score scale/output format, but output schema presumably handles that.

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 all 3 parameters are documented in the schema. The description adds the notion that checkSmtp is optional enrichment and that _payment requires a first call to obtain requirements, but the schema already explains the two-step signing flow well. The description's main added value is signaling which checks are default (syntax, MX, disposable) vs optional (SMTP).

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?

Clear specific verb (validate/verify) with resource (email address) and enumeration of what checks occur (syntax, MX records, SMTP, disposable domains, risk score). Distinct from all 11 siblings, none of which do email validation. The risk score and cost details further differentiate it.

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?

Description implies when to use (when you need to validate/verify an email) but doesn't explicitly name alternatives or exclusions. The _payment parameter details a clear two-step flow (first call without _payment, then retry with signed payload) which is valuable operational guidance. Lacks explicit 'use X instead when...' guidance but context is reasonably clear.

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