> ## Documentation Index > Fetch the complete documentation index at: https://docs.redpill.ai/llms.txt > Use this file to discover all available pages before exploring further. # Billing > Pay-as-you-go credits in USD: what a request costs, how to add credits, key budgets, and where to read usage. RedPill is pay as you go. You add credits in USD, and each request deducts its cost from the workspace's balance. ## What a request costs Cost is the model's list price times tokens. The price per token is in the model object from [`GET /v1/models`](/api-reference/models), and every response reports what it was charged: | `usage` field | Meaning | | -------------------------------------------- | -------------------------------------------------------------------------------------------- | | `cost` | Amount charged for this response, in USD. | | `prompt_tokens`, `completion_tokens` | Billed at the model's `pricing.prompt` and `pricing.completion`. | | `completion_tokens_details.reasoning_tokens` | Part of `completion_tokens`; billed at the completion rate. | | `prompt_tokens_details.cached_tokens` | Billed at `pricing.input_cache_read` when the model lists one, otherwise at the prompt rate. | A request that is rejected before reaching a model, for example by a rate limit or a routing constraint, costs nothing. ## Add credits * **Card**: pay from the [Credits](https://www.redpill.ai/credits) page, 5 to 1,000 USD per payment. * **Auto-recharge**: choose a threshold and an amount, both at least 5 USD; when the balance drops below the threshold, the amount is charged to the saved card. Invoices and payment methods are on the [Billing](https://www.redpill.ai/billing) page. ## Limits on spend Set a budget on an API key when you create it. When the key reaches its budget, or the account's quota is used up, requests return `402` with `error.type` `insufficient_quota` and a message naming which limit was hit. ## Read usage The [Usage](https://www.redpill.ai/usage) page shows daily totals and a per-request log with model, tokens, and cost, with filters. An agent can read the same data through the [MCP server](/get-started/mcp). ## Related