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

With no annotations, the description carries the full burden. It discloses that the tool creates a Stripe checkout session, explains why registrant details are required (legal ownership), notes WHOIS privacy, and lists return fields. It does not address failure modes or whether funds are charged immediately, but the core behavior is transparent.

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 long, but every section earns its place: critical warnings, parameter explanations, and return values. It front-loads the most important prerequisite. Minor redundancy exists with the repeated 'IMPORTANT' emphasis, but overall structure is clear and actionable.

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?

The description covers the complete transactional context: prerequisite check, user confirmation, registrant rationale, payment method, and required post-action. The Returns section complements the existing output schema. It does not cover error handling, but that is not critical given the rich guidance provided.

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 0%, but the Args section gives meaningful descriptions for all 11 parameters, including an example for domain, a format for phone, and explicit optionality for org_name. This fully compensates for the schema's lack of per-field documentation.

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 opens with 'Start the purchase flow for an available domain via Stripe checkout,' which clearly identifies the action, resource, and payment method. It differentiates from sibling tools like buy_domain_crypto and buy_domain_mpp by specifying Stripe, and the word 'available' implies a prerequisite check.

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?

Provides explicit, mandatory usage instructions: call check_domain first, show the price to the user, obtain explicit confirmation, and never call without approval. It also dictates the post-return action of opening the checkout_url, making the transactional flow unambiguous.

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