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

With no annotations, the description carries the full burden and does substantial work: it discloses the out-of-band email delivery of a one-time code, the required downstream verification step, the eligibility constraints, and an important capability boundary ('can buy; it cannot sell'). It stops short of stating rate limits, whether re-calling with an existing email errors or resends, or what a successful response contains.

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?

Four short sentences, front-loaded with the action, followed by the mechanics, then the constraints. No restatement of the title and no filler; each sentence conveys a distinct fact.

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 an account-provisioning tool with no annotations and no output schema, the description covers the whole flow an agent needs: request code, expect email, call verify_agent_email, respect eligibility limits. The main gap is behavior on a repeat call for an already-registered email, which matters because the description explicitly invites re-calling for a fresh code.

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 four parameters are already documented in the schema with the term URL, the 60-character cap, and the throwaway-inbox refusal. The description adds only the rationale that the email must be one 'the agent or its operator can read' in order to receive the code, which is marginal beyond the schema. Baseline 3 applies.

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 specific verb and resource ('Open a buyer account for an AI agent') and adds a second, distinct capability ('get a fresh code for one you opened') that an agent could not infer from the name alone. It is clearly separable from verify_agent_email, which it names as the follow-on step.

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 clear preconditions (operator must accept Terms and be 18+) and explicitly routes the agent to verify_agent_email after the code arrives, which is the main sequencing decision. It omits any statement about what to do if an account already exists, though the 'fresh code' phrasing partly covers re-entry.

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