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

Annotations already carry readOnlyHint=true, openWorldHint=true, idempotentHint=true, destructiveHint=false, so the safety profile is covered. The description adds genuine behavioral value beyond annotations: the tool cannot observe SMTP transport TLS or sub-domain coverage from a single scan, DNS-only results cap at INDETERMINATE (not a pass), and verdicts include a NOT MEASURED state with structured evidence. It stops short of disclosing cache behavior or rate limits, but the added constraints are materially useful.

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 dense but every sentence earns its place: purpose, output structure, key limitation, and sibling distinction. It front-loads the core purpose and scoping before the limitation and differentiation. Slightly long, but no filler.

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?

With no output schema, the description explains the return semantics well: the seven controls, the three verdict states (satisfied, not satisfied, NOT MEASURED), structured evidence, and the INDETERMINATE ceiling. Combined with fully documented parameters and safety annotations, little an agent needs to call this correctly 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%, so all three parameters (domain, format, force_refresh) are already documented in the schema. The description reinforces the domain parameter's scope with 'ONE domain' but adds little beyond that; the baseline 3 is appropriate since the schema does the heavy lifting.

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 states a specific verb and resource: 'Answer, for ONE domain, whether it meets the New Zealand Secure Government Email (SGE) requirements' with a deadline (October 2026) and lists the seven controls evaluated. It explicitly names map_compliance as the sibling it is not, so an agent can distinguish it without opening schemas.

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 clear usage context: it is scoped to ONE domain, and it explicitly names the alternative map_compliance for NIST/PCI/SOC 2/CIS mapping. It also tells the agent when the tool is insufficient — a single-domain DNS-only scan cannot observe SMTP transport TLS or sub-domain coverage and tops out at INDETERMINATE. It does not spell out when to prefer batch_scan or scan_domain, leaving that partially implicit.

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