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

With no annotations provided, the description carries the full burden of behavioral disclosure. It does this thoroughly: it discloses that registration returns an API key and payment URL, that the user MUST open the payment_url in a browser to add a credit card before API calls, the pay-per-request billing model with no monthly fee, and that no authentication is required. This goes well beyond a bare 'registers an account' and gives the agent actionable behavioral expectations.

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 front-loaded with the core purpose and outputs, then covers the critical user action and billing model. It is a bit longer than strictly necessary, but every sentence contributes useful information—especially the billing terms and the instruction to check account_status. No filler or redundancy.

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?

Given the tool itself is a simple 3-parameter registration action with no output schema, the description is complete enough for an agent to invoke it correctly and manage expectations. It spells out the outputs (API key, payment_url), the required follow-up action (open payment_url in browser), the billing mode, and authentication status. It even references account_status for accrued usage, covering the natural next step.

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?

All three parameters (name, email, password) are already fully described in the input schema with 100% coverage. The description does not add parameter-specific guidance beyond what the schema provides. Baseline 3 is appropriate because the schema already carries the semantic load here.

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 begins with a clear, specific verb and resource: 'Register a new Zyla API Hub account directly from the AI agent.' It then names the two outputs (API key and payment_url), which makes the tool's function unmistakable. This also distinguishes it from sibling tools like account_status or search_catalog, which serve different purposes.

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 provides clear context for when to use this tool: it is the account registration entry point and requires no authentication. It also explicitly routes the agent to account_status for billing details, which acts as a pointer to a sibling alternative for follow-up. It does not explicitly state 'use this instead of X,' but the purpose and post-conditions make the usage context clear.

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