Purchase email address

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

With no annotations provided, the description carries the full burden and does it well: it warns that the call immediately spends wallet funds, requires an API key, and explains the best-effort replay guard so the agent understands cost and deduplication behavior upfront.

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 compact, front-loaded with purpose and the cost warning, and every sentence contributes either a prerequisite, a hazard, or an idempotency rule. No filler or redundant schema repetition.

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 three-parameter tool with no output schema and no annotations, the description covers the essential context: what to do first, what it costs, what auth is needed, and how to avoid duplicate charges or intentionally request a second address. An agent has enough information to call it correctly.

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?

Even though schema coverage is 100%, the description adds substantial meaning beyond the schema: it explains that domain should come from email_get_domains and, more importantly, clarifies that reusing idempotency_token replays without charging while a different token intentionally orders a second address. This is exactly the kind of semantic nuance an agent needs.

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: "Reserve a temporary email address for OTP verification." It also names the prerequisite sibling (email_get_domains) and hints at the alternate behavior of email_reorder via idempotency, so it is easy to distinguish from sibling tools.

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 context: use email_get_domains first to pick site and domain, and explains how to use idempotency_token for retries vs. ordering a second address. It does not explicitly list when-not-to-use alternatives, but the guidance is specific and actionable.

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