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

With no annotations, the description carries the full burden of disclosure. It details the payment flow: accepts a PIN, issues and pays on an invoice, and either extends or creates a subscription. It also specifies the return value shape. It does not mention failure modes or whether the PIN becomes consumed, but it provides a clear and non-trivial behavioral overview beyond the schema.

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, followed by impact and usage guidance, then organized @param and @return documentation. Every sentence adds value, no filler or repetition. It manages to be thorough without being verbose, and the structure supports quick agent scanning.

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 tool with no annotations and sparse schema, the description covers the main action, the preferred use case, parameter hints, side-effect information (invoice issuance and subscription lifecycle), and return value structure. It omits error cases, prerequisites (e.g., customer existence) and whether the voucher is destroyed, but given the output schema exists and sibling context, it is reasonably complete for selection and invocation.

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?

The schema provides no descriptions (coverage 0%), but the description's @param documentation adds substantial meaning: identifier is linked to session_id/mobile number, ott_pin is typically 10 digits, and subscription_type_fk is a database number defaulting to 1. These hints go far beyond bare names and types, making parameter usage clear and actionable.

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 a specific action: 'Accepts a subscription payment using an OTT Voucher PIN.' It identifies the resource (subscription) and the method (OTT voucher), and distinguishes itself from sibling payment tools like paywall__pay_subscription_with_credits and paywall__pay_subscription_with_wallet by explicitly being the 'preferred tool' for OTT-based activation.

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 explicitly says this is the preferred tool for activating subscriptions using OTT as a payment method, giving clear usage context. It does not name alternative tools or state exclusions, but the distinction from other payment subscription tools is implied by the OTT-specific focus. This exceeds a vague hint but stops short of full alternative guidance.

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