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

The description goes beyond annotations by stating 'deterministic' and 'pure function, no DNS', which are behavioral traits not fully captured by annotations (idempotentHint, destructiveHint). It also discloses the x402-paid cost. This adds meaningful context about side effects (payment) and external dependencies (no DNS). No contradiction with annotations, though 'pure function' could be interpreted as read-only while readOnlyHint is false, the description qualifiers make it clear the computation is deterministic, not necessarily free of payment side effects.

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 extremely concise: two sentences, front-loaded with the tool name, pricing, and core functionality. Every word contributes value, with no filler or repetition. It is well-structured for quick agent consumption.

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 the presence of an output schema and fully described parameters, the description adequately covers the high-level purpose, behavior, and cost. It does not explain the payment flow or how to use apiKey vs. x402, but those are detailed in the schema. The description is sufficient for an agent to understand what the tool does and decide if it fits the use case, though a note about the batch sibling or free-tier option would increase completeness.

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?

All 13 parameters have rich descriptions in the schema (100% coverage), so the baseline is 3. The description adds little about parameters themselves, only naming output categories. It does not clarify the specific parameter semantics beyond what the schema already provides, so it neither compensates nor detracts.

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 identifies the tool as an email/contact quality scorer, listing specific outputs (validity, deliverability score, disposable/role/free classification, typo suggestion). It uses a specific verb ('scorer') and resource ('email/contact'), making the purpose clear. However, it does not explicitly distinguish itself from the sibling tool 'emailguard_validate_batch', leaving ambiguity about single vs. batch validation.

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 implicit usage context: 'Pure function, no DNS' suggests it is a fast, deterministic choice suitable for single email checks without network dependency. It also notes it is x402-paid, hinting at cost considerations. However, it does not explicitly state when to use this tool versus alternatives like the batch validator or free-tier key options, and no exclusions are mentioned.

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