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

Annotations already declare readOnlyHint=false, destructiveHint=false, openWorldHint=true, so the write/non-destructive profile is covered. The description does add real behavioral value beyond that: 'rechecks availability before saving' and 'registers only after payment clears' explain the payment gating, and the idempotency/retry guidance is useful. However much of the canonicality/idempotency/confirmation block is generic template text, and the confirmation line lists 'this read' among categories for a tool annotated as a write, which is loose but not a strict contradiction.

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 purpose is correctly front-loaded in the first sentence, but the following canonicality, idempotency and confirmation-boundary sentences are reusable template prose rather than tool-specific guidance, and the broken 'stated above' reference undercuts the structure.

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 10-parameter, nested-object, no-output-schema write tool, the description covers prerequisites, availability recheck and payment gating, which is meaningful. It is still thin on the actual save/registration flow — how quoteId and registrantReviewToken are obtained and what happens between save and registration — leaving the agent to reconstruct the pipeline from sibling names.

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 80%, so the schema already documents the nested inboxes, registrant, termYears and token parameters well. The description only gestures at them in aggregate ('registration term, inbox plan and confirmed registrant contact') without adding format, default or dependency detail, so the baseline 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?

States a concrete verb+resource: 'Save a searched domain, registration term, inbox plan and confirmed registrant contact', and the title reinforces it. It is clearly distinguishable from read-only siblings like search_company_domains or check_email_domain, though it never explicitly names the upstream search step or the downstream start_company_domain_checkout it feeds into.

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 only usage signal is 'Prerequisite: authenticated active company access plus every prerequisite stated above' — the phrase 'stated above' is dangling boilerplate with nothing preceding it, so the prerequisite chain is unusable. No alternatives or when-not-to-use conditions are offered (e.g. when to call search_company_domains first).

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