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

With no annotations, the description carries the full burden. It discloses the tool's behavior by listing the checks performed and the exact return fields, implying a read-only audit operation. It does not explicitly state that it makes network requests or has no side effects, but the nature of the tool makes this clear.

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 two sentences, front-loads the main purpose, and packs in the checks and return shape without any redundant words. Every element is useful.

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?

Despite lacking an output schema, the description supplies the return object's fields. With one well-documented parameter and clear check semantics, an agent has enough information to invoke and interpret the tool correctly. No essential invocation detail is missing.

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%; the schema already defines 'domain' as a bare domain with an example. The description does not add significant new meaning about the parameter, so the baseline of 3 is appropriate.

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 states the verb and resource: 'Audit an email domain' and enumerates specific checks (MX, SPF/DMARC/DKIM, disposable). It also specifies the return object, leaving no ambiguity about what the tool does. Although there are no sibling tools to differentiate from, the level of specificity earns a 5.

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?

There are no sibling tools, so no alternative routing is needed. The description gives clear context: 'in one call' suggests this is the comprehensive domain audit tool, and the list of checks conveys when it applies. It does not explicitly state when not to use it, so it falls short of a 5.

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