Self-register a new Verifly account + API key

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

With no annotations provided, the description fully carries the behavioral disclosure burden and does so excellently: it warns about the one-time visibility of the API key, instructs immediate capture, states it cannot be retrieved again, mentions free credits, and discloses domain rejection. These side effects go well beyond a basic creation operation.

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 three sentences, each earning its place: purpose, requirements/free credits, and critical one-time key behavior. It is front-loaded with the core action and contains no fluff or redundant filler.

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 simple 2-parameter tool with no output schema, the description covers purpose, prerequisites, response contents (account id/email and API key), and the crucial one-time-capture behavior. There is no ambiguity left for an agent to misuse the tool or lose the key.

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 100% because both parameters have descriptions in the schema (e.g., 'not a disposable domain', 'minimum 8 characters'). The description adds minimal parameter-specific meaning beyond restating these constraints; its extra value about the key pertains to the response, not the input parameters. Baseline 3 is appropriate when schema already documents parameters.

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 clearly states the tool creates a brand-new Verifly account and frames it as the self-onboarding mechanism, using the specific verb 'create' and naming the resource. It is clearly distinguished from sibling tools like get_account or buy_credits, which operate on existing accounts.

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 explicit context for when to use the tool ('this is how an agent self-onboards with no human in the loop') and notes key requirements (email/password, disposable domains rejected). However, it does not explicitly state when not to use it or compare to alternatives, though no sibling tool serves the same account-creation purpose.

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