> **For AI agents:** this page is a focused, LLM-optimized view of a
> single Fiber AI operation. Before calling it, fetch the routing
> instructions at [`https://api.fiber.ai/llms.txt`](https://api.fiber.ai/llms.txt) and the full operation
> index at [`https://api.fiber.ai/ai-docs/index.md`](https://api.fiber.ai/ai-docs/index.md).

# cardsAttach

`POST /v1/cards/attach`

**Tags:** `Account`

Attach card to trial account

**Endpoint:** `https://api.fiber.ai/v1/cards/attach`

## Description

Attach a payment card to a cardless trial organization using a single-use Stripe shared payment token. The card is verified with a temporary $1 authorization that is refunded immediately (net cost $0), and the organization's free-credit ceiling is raised. The verified card is not saved for future charges — every future paid top-up requires a freshly-minted shared payment token.

⚡ Rate limit: 3 requests per 1 minute

💰 Cost: FREE! No credits are charged for this API. ⓘ

## Request body (JSON Schema)

```json
{
  "type": "object",
  "properties": {
    "apiKey": {
      "type": "string",
      "description": "Your Fiber API key"
    },
    "sharedPaymentGrantedToken": {
      "type": "string",
      "pattern": "^spt_",
      "minLength": 1,
      "description": "Single-use Stripe shared payment token (`spt_...`) authorizing exactly one card handoff. Mint it on the buyer side (see https://docs.stripe.com/agentic-commerce/concepts/shared-payment-tokens); each request must submit a freshly-minted token."
    }
  },
  "required": [
    "apiKey",
    "sharedPaymentGrantedToken"
  ]
}
```

## Response — success (JSON Schema)

```json
{
  "type": "object",
  "properties": {
    "output": {
      "type": "object",
      "properties": {
        "status": {
          "type": "string",
          "enum": [
            "attached"
          ]
        },
        "creditsGranted": {
          "type": "integer",
          "description": "Additional free trial credits granted by this call. Zero when the organization was already at its trial credit ceiling (e.g. re-attaching after the ceiling was already reached)."
        },
        "totalCreditsUnlocked": {
          "type": "integer",
          "description": "Free trial credit ceiling after this call — the maximum credits the organization can spend on the trial before it needs a paid top-up."
        },
        "paymentMethod": {
          "type": "object",
          "properties": {
            "brand": {
              "type": [
                "string",
                "null"
              ],
              "description": "Card network (e.g. 'visa', 'mastercard'). Null when unavailable."
            },
            "last4": {
              "type": [
                "string",
                "null"
              ],
              "description": "Last four digits of the card. Null when unavailable."
            }
          },
          "description": "Display-only metadata for the card that was verified in this call. This is not a saved payment method — future paid top-ups must submit a freshly-minted shared payment token."
        }
      },
      "required": [
        "status",
        "creditsGranted",
        "totalCreditsUnlocked",
        "paymentMethod"
      ]
    },
    "chargeInfo": {
      "oneOf": [
        {
          "type": "object",
          "properties": {
            "method": {
              "type": "string",
              "enum": [
                "charged-now"
              ]
            },
            "creditsCharged": {
              "type": "number"
            },
            "lowCreditAlert": {
              "type": [
                "object",
                "null"
              ],
              "properties": {
                "getMoreCreditsUrl": {
                  "type": "string",
                  "format": "uri",
                  "description": "URL to top up credits or restart billing cycle to get fresh credits."
                },
                "message": {
                  "type": "string",
                  "description": "Human-readable credits warning."
                },
                "availableCredits": {
                  "type": "number",
                  "description": "Number of credits remaining in the current billing period."
                }
              },
              "required": [
                "getMoreCreditsUrl",
                "message",
                "availableCredits"
              ],
              "description": "Contains a link to get more credits, a warning message, and the remaining credit count."
            }
          },
          "required": [
            "method",
            "creditsCharged"
          ],
          "description": "Credits were charged immediately for this operation"
        },
        {
          "type": "object",
          "properties": {
            "method": {
              "type": "string",
              "enum": [
                "charging-later"
              ]
            },
            "message": {
              "type": "string"
            },
            "lowCreditAlert": {
              "type": [
                "object",
                "null"
              ],
              "properties": {
                "getMoreCreditsUrl": {
                  "type": "string",
                  "format": "uri",
                  "description": "URL to top up credits or restart billing cycle to get fresh credits."
                },
                "message": {
                  "type": "string",
                  "description": "Human-readable credits warning."
                },
                "availableCredits": {
                  "type": "number",
                  "description": "Number of credits remaining in the current billing period."
                }
              },
              "required": [
                "getMoreCreditsUrl",
                "message",
                "availableCredits"
              ],
              "description": "Contains a link to get more credits, a warning message, and the remaining credit count."
            }
          },
          "required": [
            "method",
            "message"
          ],
          "description": "Credits will be charged after the operation completes"
        },
        {
          "type": "object",
          "properties": {
            "method": {
              "type": "string",
              "enum": [
                "charged-for-async-process"
              ]
            },
            "creditsCharged": {
              "type": "number"
            },
            "message": {
              "type": "string"
            },
            "lowCreditAlert": {
              "type": [
                "object",
                "null"
              ],
              "properties": {
                "getMoreCreditsUrl": {
                  "type": "string",
                  "format": "uri",
                  "description": "URL to top up credits or restart billing cycle to get fresh credits."
                },
                "message": {
                  "type": "string",
                  "description": "Human-readable credits warning."
                },
                "availableCredits": {
                  "type": "number",
                  "description": "Number of credits remaining in the current billing period."
                }
              },
              "required": [
                "getMoreCreditsUrl",
                "message",
                "availableCredits"
              ],
              "description": "Contains a link to get more credits, a warning message, and the remaining credit count."
            }
          },
          "required": [
            "method",
            "creditsCharged",
            "message"
          ],
          "description": "Credits that were charged for an asynchronous operation"
        },
        {
          "type": "object",
          "properties": {
            "method": {
              "type": "string",
              "enum": [
                "free"
              ]
            },
            "message": {
              "type": "string"
            },
            "lowCreditAlert": {
              "type": [
                "object",
                "null"
              ],
              "properties": {
                "getMoreCreditsUrl": {
                  "type": "string",
                  "format": "uri",
                  "description": "URL to top up credits or restart billing cycle to get fresh credits."
                },
                "message": {
                  "type": "string",
                  "description": "Human-readable credits warning."
                },
                "availableCredits": {
                  "type": "number",
                  "description": "Number of credits remaining in the current billing period."
                }
              },
              "required": [
                "getMoreCreditsUrl",
                "message",
                "availableCredits"
              ],
              "description": "Contains a link to get more credits, a warning message, and the remaining credit count."
            }
          },
          "required": [
            "method",
            "message"
          ],
          "description": "No credits were charged for this operation"
        },
        {
          "type": "object",
          "properties": {
            "method": {
              "type": "string",
              "enum": [
                "credits-refunded"
              ]
            },
            "creditsRefunded": {
              "type": "number"
            },
            "message": {
              "type": "string"
            },
            "lowCreditAlert": {
              "type": [
                "object",
                "null"
              ],
              "properties": {
                "getMoreCreditsUrl": {
                  "type": "string",
                  "format": "uri",
                  "description": "URL to top up credits or restart billing cycle to get fresh credits."
                },
                "message": {
                  "type": "string",
                  "description": "Human-readable credits warning."
                },
                "availableCredits": {
                  "type": "number",
                  "description": "Number of credits remaining in the current billing period."
                }
              },
              "required": [
                "getMoreCreditsUrl",
                "message",
                "availableCredits"
              ],
              "description": "Contains a link to get more credits, a warning message, and the remaining credit count."
            }
          },
          "required": [
            "method",
            "creditsRefunded",
            "message"
          ],
          "description": "Credits were refunded for this operation"
        }
      ]
    },
    "warnings": {
      "type": [
        "array",
        "null"
      ],
      "items": {
        "type": "object",
        "properties": {
          "field": {
            "type": "string",
            "description": "Full path to extraneous field (e.g., 'searchParams.ExtraField')"
          },
          "message": {
            "type": "string",
            "description": "Warning message"
          }
        },
        "required": [
          "field",
          "message"
        ]
      },
      "description": "Warnings about extraneous fields in request"
    },
    "advice": {
      "type": [
        "array",
        "null"
      ],
      "items": {
        "type": "string"
      },
      "description": "Tips, recommendations, and suggestions for using this API effectively."
    }
  },
  "required": [
    "output",
    "chargeInfo"
  ],
  "additionalProperties": false
}
```

---

Canonical JSON: [`https://api.fiber.ai/openapi.json`](https://api.fiber.ai/openapi.json)
Operation index: [`https://api.fiber.ai/ai-docs/index.md`](https://api.fiber.ai/ai-docs/index.md)