> ## Documentation Index
> Fetch the complete documentation index at: https://docs.solvapay.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Plans and billing glossary

> What a credit is, how meters name usage, and the difference between included allowance and wallet coverage.

SolvaPay splits **what gets counted** from **what gets spent**. The meter supplies the display noun. Credits are only the prepaid wallet.

## Credits

A credit is a prepaid wallet unit. **100 credits = 1 USD cent.**

| Term           | Meaning                                                     |
| -------------- | ----------------------------------------------------------- |
| Credit balance | How many credits the customer holds                         |
| Top-up         | One payment that adds credits (`purpose: 'credit_topup'`)   |
| Auto-recharge  | The setting that tops up the wallet when the balance is low |

Credits are never a count of activity. Usage rates in the console and customer UI are **money per meter noun** (`$0.02 / request`). Credits stay on the balance widget and ledger.

## Meter noun

A meter defines what to count. Every provider is seeded with one meter:

| Field         | Seeded default |
| ------------- | -------------- |
| `name`        | `requests`     |
| `displayName` | Requests       |
| `unit`        | `requests`     |

MCP tool calls also record usage under `tool:{toolName}` meter names. Custom meters may use another noun (`documents`, `tokens`). Copy uses that noun: "1,000 requests included", not "1,000 units".

A usage event is one recorded data point against a meter. The HTTP path stays `POST /v1/sdk/meter-events`.

## Included vs remaining

Two leftover counts exist. Do not mix them.

| Count              | Wire field                | Meaning                                                                                 |
| ------------------ | ------------------------- | --------------------------------------------------------------------------------------- |
| Included remaining | `LimitResponse.remaining` | Leftover **included allowance** toward the plan cap. `-1` means unlimited               |
| Wallet coverage    | `remainingUnits`          | How many metered items the **credit balance** still covers (`balance / creditsPerUnit`) |

The stored included cap is `LimitOption.cap`. Copy says **included**, not "limit" or "quota".

Recurring, usage-based, hybrid, and one-time are **derived labels** from `options[]`, not stored plan types. See [Plans](/plans/overview).

`LimitOption.cap === 0` means unlimited. Commerce emits that sentinel on the wire as `freeUnits: 0`. A missing limit option is pay-as-you-go (no included allowance), not unlimited.

## Overage

Overage is usage beyond the included allowance, charged per meter noun. A plan with no included cap is pure pay-as-you-go: every counted item is billed at the per-request rate.

## Activation and paywall

`POST /v1/sdk/activate` follows the plan shape:

| Plan                                    | Result                                                            |
| --------------------------------------- | ----------------------------------------------------------------- |
| Free                                    | `activated` immediately                                           |
| Usage-based (metered, no billing cycle) | `activated` immediately. A zero balance is not an activation gate |
| Paid recurring, hybrid, or one-time     | `payment_required` — complete checkout before the plan activates  |

A usage plan's empty wallet surfaces later as `topup_required` at usage time, not at activation.

## Credit minting

Credits mint when the charge succeeds. The webhook is an idempotent backstop, not the primary booking path.

## Words to avoid

| Avoid                             | Use instead                                                  |
| --------------------------------- | ------------------------------------------------------------ |
| Units (generic)                   | The meter noun (`requests`, or the meter's `unit`)           |
| Quota                             | Included                                                     |
| Consumption (as a noun)           | Usage                                                        |
| Calls / messages (as a stand-in)  | The meter noun, unless that meter’s `unit` really is "calls" |
| Automatic top-up (on the setting) | Auto-recharge                                                |

Wire identifiers (`units`, `CHARGE_PERS = 'unit'`, `customer.credit.auto_topup_failed`) stay as published.

## Next steps

* [Plans](/plans/overview) — plan types and configuration
* [Billing](/plans/billing) — cycles, renewals, and usage on a purchase
* [Usage events](/sdks/typescript/guides/usage-events) — record usage from the TypeScript SDK