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

Annotations only indicate non-destructive and closed-world behavior. The description adds valuable context: the Stripe payment redirect, the KYC precondition, handling failed-precondition by walking through verification, and the post-payment prefilled intake. No contradiction with annotations.

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?

Three sentences, all earning their place: the first states the primary action and output, the second gives user-facing instructions, and the third adds prerequisite and post-payment context. Front-loaded and efficient.

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 an output schema exists, return-value details are not required. The description covers the KYC prerequisite, the payment flow (URL handoff and Stripe exclusivity), and post-payment behavior. Nothing critical is missing for an agent to call this 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?

Schema description coverage is 50%, and the description does not explain the parameters. 'companyId' is only described as a 'UUID value wrapper' in the schema, and 'package' has no description at all. The enum values are self-explanatory, but the description doesn't compensate for the coverage gap by explaining when to choose PREPARATION vs RENEWAL or what companyId refers to.

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 starts with a specific verb and resource: 'Starts an ITIN purchase: creates the application and returns a Stripe Checkout URL.' It clearly states the action, output, and what to do with the result, distinguishing it from siblings like itin_poll_itin_checkout or itin_get_itin_quote.

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 strong context: use when the user is purchasing an ITIN, requires prior KYC, and instructs to give the user the payment URL while keeping payment on Stripe. It doesn't explicitly name alternatives or exclusions, but the context effectively routes the agent.

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