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

Annotations already declare a non-read-only, open-world, non-idempotent mutation; the description adds real value on top by disclosing default-nameserver fallback, the wallet currency-conversion rule (only the missing amount is converted), and a gate requiring explicit user acceptance before a premium charge. It stops short of stating retry/duplicate-charge behavior or failure modes, which matters for a non-idempotent financial mutation.

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?

Front-loads the core action, then layers prerequisite, currency, wallet, and premium guidance in a sensible order with no filler sentences. It is dense and slightly long, but each sentence carries actionable workflow information rather than restating the schema.

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?

An output schema exists, so return values need no explanation, and the description covers the money-related decision path thoroughly. The remaining gap is operational safety: nothing says whether a retry double-charges or what valid period_years values are, which is a meaningful omission for an irreversible purchase with six parameters.

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 0%, so the description must carry the load, and it does for four of six parameters: nameservers (omitted → account default), contact_handle (one reusable contact for all four roles), currency (must match the USD/EUR quote), and allow_premium (gated on user acceptance of the premium quote). It adds nothing about domain format or period_years bounds, leaving one required parameter entirely unexplained.

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?

Opens with a concrete verb+resource: 'Register a domain through AIvikings', and the remaining sentences make clear this is a new registration workflow, distinguishing it implicitly from domain_transfer and renew_domain. It never explicitly says 'not for transfers/renewals', so it falls just short of the sibling-differentiation bar for 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?

Gives an explicit ordered workflow: call list_domain_registration_contacts first, create_contact if no registration-ready contact exists, and only set allow_premium=true after the user explicitly accepts the get_domain_pricing quote. It names the alternative tools and the condition that selects each, so the agent has no ambiguity about sequencing.

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