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

Goes well beyond the annotations: it discloses the no-charge/no-company-creation semantics, the OTP expiry (10 minutes), guess limits and single-use behavior, token expiry (~15 minutes), and the MCP auth prerequisite (Bearer aa_... or OAuth token). Annotations only give safe-mutation hints; the description carries the real behavioral load.

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?

Front-loaded with the purpose and the non-charge caveat, then walks the numbered steps in order. It is dense and long, but nearly every clause carries operational information; the REST-vs-MCP aside is the only part that could be tightened.

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 multi-step, no-output-schema onboarding tool with an auth prerequisite, the description covers inputs, returns (bootstrapToken, expiresIn), expiry windows, and the downstream call path. Nothing an agent needs to invoke it correctly is missing.

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% and the field descriptions already state the per-call rules (code omitted first call, required second; disposable domains rejected; company_name stored on the JWT). The description repeats this rather than adding new syntax or format detail, so baseline 3 is correct.

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 ('Start zero-human company onboarding from a contact email') and immediately bounds the scope ('Does not charge or create a company'). An agent can distinguish it from the billing_* siblings without opening any schema.

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?

Explicitly lays out the two-step call sequence, names the condition that switches to the REST alternative ('When you have no aa_ key yet'), and routes to the follow-up tools (billing_machine_pay / billing_checkout) after bootstrap. No condition is left to inference.

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