---
title: "The Seller API: public WhatsApp cost API"
description: "The Seller's free public API to estimate the cost of WhatsApp Official API messages in Brazil, with an OpenAPI spec, examples and error format."
url: https://www.theseller.com.br/en/developers
lang: en
---

DEVELOPERS

# The Seller API

A free, public API with no authentication to estimate how much it costs to send messages through the Official WhatsApp API in Brazil. It uses the same rate card as our calculator: Meta's fee by category, volume tiers and The Seller's per-message fee.

[OpenAPI 3.1 specification](https://www.theseller.com.br/openapi.json) [llms.txt for AI agents](https://www.theseller.com.br/llms.txt)

## Endpoints

Base URL: `https://www.theseller.com.br`

Authentication: none. JSON responses with CORS enabled.

### Estimate message cost

GET /api/v1/whatsapp-pricing/simulate

Calculates Meta's fee (with volume tiers), The Seller's fee and the total and average cost per message, in Brazilian reais.

#### Parameters

- `quantity`: required. Number of messages (1 to 1,000,000,000).
- `category`: marketing (default), utility or authentication.
- `currency`: Meta account currency: BRL (default) or USD.
- `exchangeRate`: BRL per USD, used when currency=USD. Default 5.4.

```
curl "https://www.theseller.com.br/api/v1/whatsapp-pricing/simulate?quantity=10000&category=marketing"
```

### Rate card

GET /api/v1/whatsapp-pricing/rates

Returns Meta's list rates and volume tiers for Brazil, The Seller's fee and the official sources.

```
curl "https://www.theseller.com.br/api/v1/whatsapp-pricing/rates"
```

## Example response

```
{
  "input": {
    "quantity": 10000,
    "category": "marketing",
    "currency": "BRL",
    "exchangeRate": 5.4,
    "market": "brazil"
  },
  "meta": {
    "currency": "BRL",
    "cost": 3217,
    "costBRL": 3217,
    "effectiveRate": 0.3217,
    "tiers": [
      {
        "quantity": 10000,
        "rate": 0.3217,
        "cost": 3217,
        "from": 1,
        "to": 10000
      }
    ]
  },
  "theSeller": {
    "ratePerMessageBRL": 0.1,
    "costBRL": 1000
  },
  "totalCostBRL": 4217,
  "averageCostPerMessageBRL": 0.4217,
  "rateCardUpdatedAt": "setembro de 2026",
  "notes": [
    "Estimate only. Meta bills its fee directly in the account currency; the final amount depends on Meta's rate card on the billing date.",
    "Service (user-initiated) conversations are not included."
  ]
}
```

## Errors

Errors are always JSON, with a stable code, a message, a hint on how to fix the request and a link to these docs. Codes: invalid_parameter and missing_parameter (400), not_found (404) and method_not_allowed (405).

```
{
  "error": {
    "code": "invalid_parameter",
    "message": "category must be one of: marketing, utility, authentication.",
    "hint": "Use the Meta template category of the message.",
    "docs": "https://www.theseller.com.br/developers",
    "parameter": "category"
  }
}
```

## Platform API

The API to connect your systems to The Seller platform is part of the Prime plan. For access and documentation, talk to our team.
[Talk to our team](https://www.theseller.com.br/en/contact)

Sales operations on WhatsApp. Official API, AI agents and automations working together so your business sells every single day.

### Product

- [Features](https://www.theseller.com.br/en/features)
- [Pricing](https://www.theseller.com.br/en/pricing)
- [Calculator](https://www.theseller.com.br/en/calculator)
- [Integrations](https://www.theseller.com.br/en/integrations)
- [Industries](https://www.theseller.com.br/en/industries)
- [Developer API](https://www.theseller.com.br/en/developers)

### Company

- [About](https://www.theseller.com.br/en/about)
- [Contact](https://www.theseller.com.br/en/contact)
- [Case studies](https://www.theseller.com.br/en/case-studies)
- [Privacy Policy](https://www.theseller.com.br/en/privacy-policy)
- [Terms of Use](https://www.theseller.com.br/termos-de-uso)

### Contact

- [(34) 8440-0300](tel:+553484400300)
- [contato@theseller.com.br](mailto:contato@theseller.com.br)
- Uberlândia, MG, Brazil

© 2026 The Seller. All rights reserved. · THE SELLER LTDA · CNPJ 61.664.493/0001-59

Meta Business Partner · Official WhatsApp API