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

No annotations are provided, so the description carries the full behavioral burden. It usefully discloses the success flow (invoice issuance and subscription creation/extension), but omits authentication requirements, voucher single-use semantics, idempotency, error behavior, and reversibility for a payment mutation.

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 purpose and success flow are front-loaded, followed by parameter and return annotations. The length is justified by the empty schema descriptions, and no sentence is clearly redundant, though the @param-style structure is somewhat mechanical.

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 payment mutation with no annotations, no output schema, and 0% schema description coverage, the description covers purpose, success flow, parameters, and return shape. It still omits prerequisites, authentication needs, error cases, and enough return detail, leaving clear gaps.

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 0%, so the description must compensate. It documents all three parameters with useful semantics: identifier hint (session_id is normally the mobile number), ott_pin format (typically a 10-digit number), and subscription_type_fk behavior (database value starting at 1, defaults to 1).

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 action: accepts a subscription payment via OTT Voucher PIN, then issues and pays an invoice that extends or creates a subscription. It also names the payment method and preferred status, which distinguishes it from sibling payment tools like pay_subscription_with_credits and pay_subscription_with_wallet.

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 says this is the preferred tool for activating subscriptions using OTT as a payment method, giving clear context for selection. It does not, however, state when not to use it or name the alternative sibling tools for other payment methods.

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