Your customers and their credits

A customer here is a customer of your own product, named by the id your system gives them. Slen keeps credit accounts for your customers, takes credits from them when a flow runs for them, and refuses a run they cannot pay for. The operations of this page add and remove customers, set up their accounts, move their credits, block a customer and set what an operation costs in credits. The console shows the same customers on Customers.

Customers and accounts

• A customer is named by external_user_id, the same id a request that runs a flow sends in context.user_id. It is an opaque id of your own, not an e-mail address or a name.

• PUT /v1/customers/{externalUserId} adds a customer without credits and without an account. It answers 201 when it created the customer and 200 when the customer was already there, so a repeat needs no key.

• An account belongs to one customer and one credit type. A credit type is a name of your own, and without one it is default. A customer with two credit types has two accounts.

• An account is created by the first top-up of its credit type or by its settings. A charge and an adjustment create nothing.

• An account carries balance, reserved and available. reserved is what running calls hold, and available is balance minus reserved.

• A customer the project has never seen answers 404 with the code customer_not_found. A customer without accounts answers with an empty accounts.

Reading takes customers:read, and every change takes customers:write, except setting a price, which takes management:write. A key of your application with gateway:write and customers:write runs flows and keeps its customers, and changes nothing else.

The settings of an account

PUT /v1/customers/{externalUserId}/accounts/{creditType} sets both settings of an account at once. It creates the customer and the account when they are missing and answers 201, and otherwise it changes the settings and answers 200.

• allow_negative lets the account go below zero. It is off by default, and then a hold or a charge the account cannot cover is refused with insufficient_credits. It can be switched off while the balance is below zero: the guard holds from the next movement.

• low_balance_threshold sets the level of the customer.balance_low webhook event. The event is sent when a movement takes available from that level or above it to below it. Zero, the default, switches the event off.

• A top-up and an adjustment do not change the settings: a body that names either field is refused with 422.

How a run spends credits

A run spends credits when it names a customer in context.user_id and the project has a credit price for its operation. context.credit_type names the credit type, and without it the type is default. The credit type decides which account pays and which price applies.

• An operation without a price for that credit type, or with a price of zero, takes no credits.

• Each model call of the run holds the price on the account before the model is called. When the call is settled, the hold becomes spend, and a call that failed gives it back.

• An account that cannot cover the price refuses the call with the code insufficient_credits. A customer who has no account of the credit type is refused the same way.

• A customer the project does not know is refused with the code customer_not_found.

• A blocked customer is refused with the code customer_blocked — Block a customer.

A price is set for an operation code and a credit type, and the next hold uses it. Setting a price again replaces it, and a hold already taken keeps the price it was taken at.

Move credits

Three operations move credits. Each requires an Idempotency-Key header of at most 190 characters, and a request without it answers 400 with the code idempotency_key_required.

• A top-up adds credits. It creates the customer and the account when they are missing.

• A charge takes credits for something your application sells by itself — an export, a seat. The statement shows it as a charge. A customer the project does not know answers 404 with the code customer_not_found, and a customer without an account of the credit type answers 402 with the code insufficient_credits.

• An adjustment corrects a balance. Its credits is signed, and zero is refused. An account that does not exist answers 404 with the code customer_not_found.

What the three share:

• credits has at most four digits after the point. A fifth digit is refused with 422, not rounded.

• note, up to 255 characters, is written on the entry and shown in the statement: an invoice number, a reason.

• A charge or an adjustment cannot take the balance below what the account holds, unless the account allows a negative balance. Such a request answers 402 with the code insufficient_credits. A top-up is never refused this way, also on an account below zero.

• A blocked customer can be topped up, charged and adjusted.

• A charge is not spend: the margin report sets the credits of a call against what the call cost, and no call stands behind a charge.

A repeat under the key moves nothing.

• Repeating the same request under its key answers 200. For 24 hours, unless the service is set up otherwise, the answer is the first one, with the balance of that moment. After that it is the account as it is now.

• A key that already names another top-up, charge or adjustment of the project answers 409 with the code idempotency_conflict. For those 24 hours any other body under the key is another request, another note too. After that another customer, another credit type, another kind of movement or another amount is another movement. A new movement needs a new key.

• A refused movement is not kept: the same request may be sent again under its key.

Block a customer

POST /v1/customers/{externalUserId}/block blocks a customer, and POST /v1/customers/{externalUserId}/unblock lets them in again.

• A new run of a blocked customer is refused with 403 and the code customer_blocked before anything is created.

• A run of theirs that is already under way — queued, or waiting for an approval — is refused at the next hold of credits of a model call. The model node leaves through Deny, and without a branch there the execution ends rejected with customer_blocked. A run of an operation without a credit price holds no credits and runs to its end.

• A repeat of a request under a key it was sent with before the block is answered with that execution.

• Credits still move, the settings still change and the statement still reads, so you can settle with a blocked customer.

• blocked_at is the moment of the first block. Blocking again keeps it and replaces block_reason only when a reason is sent. Unblocking clears both.

Delete a customer

DELETE /v1/customers/{externalUserId} removes a customer and their accounts only when nothing ever happened to them: every account is at zero with nothing held, and the statement has no entry. Otherwise the customer stays, and the answer explains why.

{
  "error": {
    "code": "customer_has_history",
    "message": "The customer has credits or a credit history and cannot be deleted; block it instead",
    "request_id": "5d8a3f1c-2b6e-4c9a-8f17-3e0b9d4c6a25"
  }
}

The statement explains the balance, so it is kept. Block such a customer instead. A delete and a movement of the same customer never pass each other: a delete that meets a top-up under way waits and then refuses, and a top-up that meets a delete under way waits and then creates the customer again.

Read customers and statements

• The list is paged, newest customer first, and each customer comes with all their accounts. status keeps the active or the blocked customers, q the customers whose external_user_id contains it, and credit_type those with an account of that credit type.

• low_balance is a number and not a flag: it keeps the customers with an account whose available is below it — an account of credit_type when both are sent. The filters choose customers and never shorten the list of their accounts.

• The statement of a customer lists every movement of their credits, newest first. An entry carries the account as the movement left it, in balance_after and available_after, and the note of the request. entry_type keeps one kind of movement, and credit_type the movements of one account. A customer without accounts has an empty statement.

Do not add credits up to get what a customer spent. A call that spent credits has two negative entries of the same price, its hold and its commit, and only the commit entries are spend.

Operations

{
  "data": [
    {
      "customer_id": "74438200973594624",
      "external_user_id": "user_8421",
      "status": "active",
      "blocked_at": "2026-10-02T09:30:00Z",
      "block_reason": "string",
      "accounts": [
        {
          "customer_account_id": "74438200973594624",
          "customer_id": "74438200973594624",
          "project_id": "74438200973594624",
          "external_user_id": "user_8421",
          "credit_type": "default",
          "balance": "12.5000",
          "reserved": "12.5000",
          "available": "12.5000",
          "allow_negative": true,
          "low_balance_threshold": "12.5000",
          "created_at": "2026-10-02T09:30:00Z",
          "updated_at": "2026-10-02T09:30:00Z"
        }
      ],
      "created_at": "2026-10-02T09:30:00Z",
      "updated_at": "2026-10-02T09:30:00Z"
    }
  ],
  "meta": {
    "limit": 1,
    "next_cursor": "string"
  }
}

{
  "data": {
    "customer_id": "74438200973594624",
    "external_user_id": "user_8421",
    "status": "active",
    "blocked_at": "2026-10-02T09:30:00Z",
    "block_reason": "string",
    "accounts": [
      {
        "customer_account_id": "74438200973594624",
        "customer_id": "74438200973594624",
        "project_id": "74438200973594624",
        "external_user_id": "user_8421",
        "credit_type": "default",
        "balance": "12.5000",
        "reserved": "12.5000",
        "available": "12.5000",
        "allow_negative": true,
        "low_balance_threshold": "12.5000",
        "created_at": "2026-10-02T09:30:00Z",
        "updated_at": "2026-10-02T09:30:00Z"
      }
    ],
    "created_at": "2026-10-02T09:30:00Z",
    "updated_at": "2026-10-02T09:30:00Z"
  }
}

{}

{
  "data": {
    "customer_id": "74438200973594624",
    "external_user_id": "user_8421",
    "status": "active",
    "blocked_at": "2026-10-02T09:30:00Z",
    "block_reason": "string",
    "accounts": [
      {
        "customer_account_id": "74438200973594624",
        "customer_id": "74438200973594624",
        "project_id": "74438200973594624",
        "external_user_id": "user_8421",
        "credit_type": "default",
        "balance": "12.5000",
        "reserved": "12.5000",
        "available": "12.5000",
        "allow_negative": true,
        "low_balance_threshold": "12.5000",
        "created_at": "2026-10-02T09:30:00Z",
        "updated_at": "2026-10-02T09:30:00Z"
      }
    ],
    "created_at": "2026-10-02T09:30:00Z",
    "updated_at": "2026-10-02T09:30:00Z"
  }
}

{
  "data": {
    "customer_id": "74438200973594624",
    "external_user_id": "user_8421",
    "status": "active",
    "blocked_at": "2026-10-02T09:30:00Z",
    "block_reason": "string",
    "accounts": [
      {
        "customer_account_id": "74438200973594624",
        "customer_id": "74438200973594624",
        "project_id": "74438200973594624",
        "external_user_id": "user_8421",
        "credit_type": "default",
        "balance": "12.5000",
        "reserved": "12.5000",
        "available": "12.5000",
        "allow_negative": true,
        "low_balance_threshold": "12.5000",
        "created_at": "2026-10-02T09:30:00Z",
        "updated_at": "2026-10-02T09:30:00Z"
      }
    ],
    "created_at": "2026-10-02T09:30:00Z",
    "updated_at": "2026-10-02T09:30:00Z"
  }
}

{
  "allow_negative": true,
  "low_balance_threshold": "12.5000"
}

{
  "data": {
    "customer_account_id": "74438200973594624",
    "customer_id": "74438200973594624",
    "project_id": "74438200973594624",
    "external_user_id": "user_8421",
    "credit_type": "default",
    "balance": "12.5000",
    "reserved": "12.5000",
    "available": "12.5000",
    "allow_negative": true,
    "low_balance_threshold": "12.5000",
    "created_at": "2026-10-02T09:30:00Z",
    "updated_at": "2026-10-02T09:30:00Z"
  }
}

{
  "data": {
    "customer_account_id": "74438200973594624",
    "customer_id": "74438200973594624",
    "project_id": "74438200973594624",
    "external_user_id": "user_8421",
    "credit_type": "default",
    "balance": "12.5000",
    "reserved": "12.5000",
    "available": "12.5000",
    "allow_negative": true,
    "low_balance_threshold": "12.5000",
    "created_at": "2026-10-02T09:30:00Z",
    "updated_at": "2026-10-02T09:30:00Z"
  }
}

{
  "reason": "string"
}

{
  "data": {
    "customer_id": "74438200973594624",
    "external_user_id": "user_8421",
    "status": "active",
    "blocked_at": "2026-10-02T09:30:00Z",
    "block_reason": "string",
    "accounts": [
      {
        "customer_account_id": "74438200973594624",
        "customer_id": "74438200973594624",
        "project_id": "74438200973594624",
        "external_user_id": "user_8421",
        "credit_type": "default",
        "balance": "12.5000",
        "reserved": "12.5000",
        "available": "12.5000",
        "allow_negative": true,
        "low_balance_threshold": "12.5000",
        "created_at": "2026-10-02T09:30:00Z",
        "updated_at": "2026-10-02T09:30:00Z"
      }
    ],
    "created_at": "2026-10-02T09:30:00Z",
    "updated_at": "2026-10-02T09:30:00Z"
  }
}

{}

{
  "data": {
    "customer_id": "74438200973594624",
    "external_user_id": "user_8421",
    "status": "active",
    "blocked_at": "2026-10-02T09:30:00Z",
    "block_reason": "string",
    "accounts": [
      {
        "customer_account_id": "74438200973594624",
        "customer_id": "74438200973594624",
        "project_id": "74438200973594624",
        "external_user_id": "user_8421",
        "credit_type": "default",
        "balance": "12.5000",
        "reserved": "12.5000",
        "available": "12.5000",
        "allow_negative": true,
        "low_balance_threshold": "12.5000",
        "created_at": "2026-10-02T09:30:00Z",
        "updated_at": "2026-10-02T09:30:00Z"
      }
    ],
    "created_at": "2026-10-02T09:30:00Z",
    "updated_at": "2026-10-02T09:30:00Z"
  }
}

{
  "data": [
    {
      "entry_id": "74438200973594624",
      "customer_account_id": "74438200973594624",
      "external_user_id": "user_8421",
      "credit_type": "default",
      "entry_type": "hold",
      "credits": "12.5000",
      "balance_after": "12.5000",
      "available_after": "12.5000",
      "reservation_id": "74438200973594624",
      "note": "string",
      "created_at": "2026-10-02T09:30:00Z"
    }
  ],
  "meta": {
    "limit": 1,
    "next_cursor": "string"
  }
}

{
  "credits": "12.5000",
  "credit_type": "default",
  "note": "string"
}

{
  "data": {
    "customer_account_id": "74438200973594624",
    "customer_id": "74438200973594624",
    "project_id": "74438200973594624",
    "external_user_id": "user_8421",
    "credit_type": "default",
    "balance": "12.5000",
    "reserved": "12.5000",
    "available": "12.5000",
    "allow_negative": true,
    "low_balance_threshold": "12.5000",
    "created_at": "2026-10-02T09:30:00Z",
    "updated_at": "2026-10-02T09:30:00Z"
  }
}

{
  "credits": "12.5000",
  "credit_type": "default",
  "note": "string"
}

{
  "data": {
    "customer_account_id": "74438200973594624",
    "customer_id": "74438200973594624",
    "project_id": "74438200973594624",
    "external_user_id": "user_8421",
    "credit_type": "default",
    "balance": "12.5000",
    "reserved": "12.5000",
    "available": "12.5000",
    "allow_negative": true,
    "low_balance_threshold": "12.5000",
    "created_at": "2026-10-02T09:30:00Z",
    "updated_at": "2026-10-02T09:30:00Z"
  }
}

{
  "credits": "12.5000",
  "credit_type": "default",
  "note": "string"
}

{
  "data": {
    "customer_account_id": "74438200973594624",
    "customer_id": "74438200973594624",
    "project_id": "74438200973594624",
    "external_user_id": "user_8421",
    "credit_type": "default",
    "balance": "12.5000",
    "reserved": "12.5000",
    "available": "12.5000",
    "allow_negative": true,
    "low_balance_threshold": "12.5000",
    "created_at": "2026-10-02T09:30:00Z",
    "updated_at": "2026-10-02T09:30:00Z"
  }
}

{
  "data": [
    {
      "credit_price_id": "74438200973594624",
      "project_id": "74438200973594624",
      "operation_code": "generate_email",
      "credit_type": "default",
      "credits": "12.5000",
      "created_at": "2026-10-02T09:30:00Z",
      "updated_at": "2026-10-02T09:30:00Z"
    }
  ]
}

{
  "operation_code": "generate_email",
  "credits": "12.5000",
  "credit_type": "default"
}

{
  "data": {
    "credit_price_id": "74438200973594624",
    "project_id": "74438200973594624",
    "operation_code": "generate_email",
    "credit_type": "default",
    "credits": "12.5000",
    "created_at": "2026-10-02T09:30:00Z",
    "updated_at": "2026-10-02T09:30:00Z"
  }
}

Examples

Find the customers who run low

low_balance keeps the customers with an account that has fewer than 20 credits available. This customer has 18 on the balance, and 4 of them are held.

curl "https://api.slen.ai/api/v1/customers?low_balance=20" \
  -H "Authorization: Bearer $SLEN_API_KEY"

{
  "data": [
    {
      "customer_id": "74439840149372928",
      "external_user_id": "user_3107",
      "status": "active",
      "blocked_at": null,
      "block_reason": null,
      "accounts": [
        {
          "customer_account_id": "74439840153567232",
          "customer_id": "74439840149372928",
          "project_id": "74438200973594624",
          "external_user_id": "user_3107",
          "credit_type": "default",
          "balance": "18.0000",
          "reserved": "4.0000",
          "available": "14.0000",
          "allow_negative": false,
          "low_balance_threshold": "0.0000",
          "created_at": "2026-09-28T11:02:17+00:00",
          "updated_at": "2026-10-02T08:39:51+00:00"
        }
      ],
      "created_at": "2026-09-28T11:02:17+00:00",
      "updated_at": "2026-10-02T08:39:51+00:00"
    }
  ],
  "meta": {
    "limit": 50,
    "next_cursor": null
  }
}

Read a customer

The customer has one account, of the credit type default. A movement that takes its available below 10 sends customer.balance_low.

curl https://api.slen.ai/api/v1/customers/user_8421 \
  -H "Authorization: Bearer $SLEN_API_KEY"

{
  "data": {
    "customer_id": "74439117522108416",
    "external_user_id": "user_8421",
    "status": "active",
    "blocked_at": null,
    "block_reason": null,
    "accounts": [
      {
        "customer_account_id": "74439117526302720",
        "customer_id": "74439117522108416",
        "project_id": "74438200973594624",
        "external_user_id": "user_8421",
        "credit_type": "default",
        "balance": "82.5000",
        "reserved": "0.0000",
        "available": "82.5000",
        "allow_negative": false,
        "low_balance_threshold": "10.0000",
        "created_at": "2026-10-02T08:40:30+00:00",
        "updated_at": "2026-10-02T09:20:05+00:00"
      }
    ],
    "created_at": "2026-10-02T08:40:00+00:00",
    "updated_at": "2026-10-02T08:40:00+00:00"
  }
}

Add a customer

The body is empty. The customer is new, so the answer is 201, and accounts is empty until a top-up or the settings create one.

curl -X PUT https://api.slen.ai/api/v1/customers/user_8421 \
  -H "Authorization: Bearer $SLEN_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{}'

{
  "data": {
    "customer_id": "74439117522108416",
    "external_user_id": "user_8421",
    "status": "active",
    "blocked_at": null,
    "block_reason": null,
    "accounts": [],
    "created_at": "2026-10-02T08:40:00+00:00",
    "updated_at": "2026-10-02T08:40:00+00:00"
  }
}

Delete a customer

This customer was added and never topped up, so the customer goes. The answer has no body.

curl -X DELETE https://api.slen.ai/api/v1/customers/user_9050 \
  -H "Authorization: Bearer $SLEN_API_KEY"

Set up an account

The settings create the account of the credit type default with a warning below 10 credits. The account cannot go below zero.

curl -X PUT https://api.slen.ai/api/v1/customers/user_8421/accounts/default \
  -H "Authorization: Bearer $SLEN_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "allow_negative": false,
    "low_balance_threshold": "10"
  }'

{
  "data": {
    "customer_account_id": "74439117526302720",
    "customer_id": "74439117522108416",
    "project_id": "74438200973594624",
    "external_user_id": "user_8421",
    "credit_type": "default",
    "balance": "0.0000",
    "reserved": "0.0000",
    "available": "0.0000",
    "allow_negative": false,
    "low_balance_threshold": "10.0000",
    "created_at": "2026-10-02T08:40:30+00:00",
    "updated_at": "2026-10-02T08:40:30+00:00"
  }
}

Block a customer

The reason is shown as block_reason. The accounts keep their credits.

curl https://api.slen.ai/api/v1/customers/user_8421/block \
  -H "Authorization: Bearer $SLEN_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "reason": "Chargeback on invoice 1042"
  }'

{
  "data": {
    "customer_id": "74439117522108416",
    "external_user_id": "user_8421",
    "status": "blocked",
    "blocked_at": "2026-10-02T09:31:10+00:00",
    "block_reason": "Chargeback on invoice 1042",
    "accounts": [
      {
        "customer_account_id": "74439117526302720",
        "customer_id": "74439117522108416",
        "project_id": "74438200973594624",
        "external_user_id": "user_8421",
        "credit_type": "default",
        "balance": "82.5000",
        "reserved": "0.0000",
        "available": "82.5000",
        "allow_negative": false,
        "low_balance_threshold": "10.0000",
        "created_at": "2026-10-02T08:40:30+00:00",
        "updated_at": "2026-10-02T09:20:05+00:00"
      }
    ],
    "created_at": "2026-10-02T08:40:00+00:00",
    "updated_at": "2026-10-02T09:31:10+00:00"
  }
}

Unblock a customer

The request has no body. The customer is active again, and blocked_at and block_reason are cleared.

curl -X POST https://api.slen.ai/api/v1/customers/user_8421/unblock \
  -H "Authorization: Bearer $SLEN_API_KEY"

{
  "data": {
    "customer_id": "74439117522108416",
    "external_user_id": "user_8421",
    "status": "active",
    "blocked_at": null,
    "block_reason": null,
    "accounts": [
      {
        "customer_account_id": "74439117526302720",
        "customer_id": "74439117522108416",
        "project_id": "74438200973594624",
        "external_user_id": "user_8421",
        "credit_type": "default",
        "balance": "82.5000",
        "reserved": "0.0000",
        "available": "82.5000",
        "allow_negative": false,
        "low_balance_threshold": "10.0000",
        "created_at": "2026-10-02T08:40:30+00:00",
        "updated_at": "2026-10-02T09:20:05+00:00"
      }
    ],
    "created_at": "2026-10-02T08:40:00+00:00",
    "updated_at": "2026-10-02T10:02:00+00:00"
  }
}

Read a customer's statement

The answer holds three movements, newest first: a charge for an export, an adjustment that took 12.5 credits, and the top-up before them.

curl https://api.slen.ai/api/v1/customers/user_8421/entries \
  -H "Authorization: Bearer $SLEN_API_KEY"

{
  "data": [
    {
      "entry_id": "74439673397166080",
      "customer_account_id": "74439117526302720",
      "external_user_id": "user_8421",
      "credit_type": "default",
      "entry_type": "charge",
      "credits": "-5.0000",
      "balance_after": "82.5000",
      "available_after": "82.5000",
      "reservation_id": null,
      "note": "PDF export 311",
      "created_at": "2026-10-02T09:20:05+00:00"
    },
    {
      "entry_id": "74439652312547328",
      "customer_account_id": "74439117526302720",
      "external_user_id": "user_8421",
      "credit_type": "default",
      "entry_type": "adjust",
      "credits": "-12.5000",
      "balance_after": "87.5000",
      "available_after": "87.5000",
      "reservation_id": null,
      "note": null,
      "created_at": "2026-10-02T09:15:42+00:00"
    },
    {
      "entry_id": "74439117530497024",
      "customer_account_id": "74439117526302720",
      "external_user_id": "user_8421",
      "credit_type": "default",
      "entry_type": "topup",
      "credits": "100.0000",
      "balance_after": "100.0000",
      "available_after": "100.0000",
      "reservation_id": null,
      "note": "Invoice 1042",
      "created_at": "2026-10-02T08:41:00+00:00"
    }
  ],
  "meta": {
    "limit": 30,
    "next_cursor": null
  }
}

Top up a customer

The key names this top-up, and a repeat under the same key adds nothing. The note names the invoice it was paid by.

curl https://api.slen.ai/api/v1/customers/user_8421/topup \
  -H "Authorization: Bearer $SLEN_API_KEY" \
  -H "Idempotency-Key: topup-user_8421-invoice-1042" \
  -H "Content-Type: application/json" \
  -d '{
    "credits": "100",
    "note": "Invoice 1042"
  }'

{
  "data": {
    "customer_account_id": "74439117526302720",
    "customer_id": "74439117522108416",
    "project_id": "74438200973594624",
    "external_user_id": "user_8421",
    "credit_type": "default",
    "balance": "100.0000",
    "reserved": "0.0000",
    "available": "100.0000",
    "allow_negative": false,
    "low_balance_threshold": "10.0000",
    "created_at": "2026-10-02T08:40:30+00:00",
    "updated_at": "2026-10-02T08:41:00+00:00"
  }
}

Adjust a balance

A negative amount takes credits away.

curl https://api.slen.ai/api/v1/customers/user_8421/adjust \
  -H "Authorization: Bearer $SLEN_API_KEY" \
  -H "Idempotency-Key: adjust-user_8421-refund-77" \
  -H "Content-Type: application/json" \
  -d '{
    "credits": "-12.5"
  }'

{
  "data": {
    "customer_account_id": "74439117526302720",
    "customer_id": "74439117522108416",
    "project_id": "74438200973594624",
    "external_user_id": "user_8421",
    "credit_type": "default",
    "balance": "87.5000",
    "reserved": "0.0000",
    "available": "87.5000",
    "allow_negative": false,
    "low_balance_threshold": "10.0000",
    "created_at": "2026-10-02T08:40:30+00:00",
    "updated_at": "2026-10-02T09:15:42+00:00"
  }
}

Charge a customer

Your application takes 5 credits for an export it made. The key names the export, so a repeat takes nothing more.

curl https://api.slen.ai/api/v1/customers/user_8421/charge \
  -H "Authorization: Bearer $SLEN_API_KEY" \
  -H "Idempotency-Key: charge-user_8421-export-311" \
  -H "Content-Type: application/json" \
  -d '{
    "credits": "5",
    "note": "PDF export 311"
  }'

{
  "data": {
    "customer_account_id": "74439117526302720",
    "customer_id": "74439117522108416",
    "project_id": "74438200973594624",
    "external_user_id": "user_8421",
    "credit_type": "default",
    "balance": "82.5000",
    "reserved": "0.0000",
    "available": "82.5000",
    "allow_negative": false,
    "low_balance_threshold": "10.0000",
    "created_at": "2026-10-02T08:40:30+00:00",
    "updated_at": "2026-10-02T09:20:05+00:00"
  }
}

List the credit prices

The project has one price.

curl https://api.slen.ai/api/v1/credit-prices \
  -H "Authorization: Bearer $SLEN_API_KEY"

{
  "data": [
    {
      "credit_price_id": "74440031913676800",
      "project_id": "74438200973594624",
      "operation_code": "generate_email",
      "credit_type": "default",
      "credits": "2.0000",
      "created_at": "2026-10-02T08:30:00+00:00",
      "updated_at": "2026-10-02T08:30:00+00:00"
    }
  ]
}

Set a credit price

From the next hold on, one model call of the operation costs a customer two credits.

curl -X PUT https://api.slen.ai/api/v1/credit-prices \
  -H "Authorization: Bearer $SLEN_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "operation_code": "generate_email",
    "credits": "2"
  }'

{
  "data": {
    "credit_price_id": "74440031913676800",
    "project_id": "74438200973594624",
    "operation_code": "generate_email",
    "credit_type": "default",
    "credits": "2.0000",
    "created_at": "2026-10-02T08:30:00+00:00",
    "updated_at": "2026-10-02T08:30:00+00:00"
  }
}

Where to go next

• Customer credits — the same customers in the console.

• Customers and credits — the same operations from the SDK.

• Analytics — the credits your customers were charged, against what their calls cost.

• Authentication — the scopes a key needs to read and to change customers.

• Overview — how credits are written in a request and in an answer.

• Error codes — every code of the API, what it means and what to do about it.

• Webhooks — how customer.balance_low arrives.