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API Reference

The Nickel API is organized around REST. Our API has predictable resource-oriented URLs, accepts JSON-encoded request bodies, returns JSON-encoded responses, and uses standard HTTP response codes, authentication, and verbs.

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Authorization and Testing

The Nickel API uses Bearer Authentication. You will be provided with a pair of API keys: one for production and one for sandbox testing.
EnvironmentBase URL
Productionhttps://rest.nickel.com
Sandboxhttps://rest.staging.nickel.com
Include your API key in the Authorization header of every request: 
Authorization: Bearer YOUR_API_KEY

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Requests and Responses

For POST requests, set the Content-Type header to application/json and pass parameters in the JSON request body. For GET requests, pass parameters as query string parameters in the URL. All API responses return application/json.

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Errors

The Nickel API uses standard HTTP response codes to indicate the success or failure of a request.
  • 2xx — Success
  • 4xx — Client error (invalid request, authentication failure, etc.)
  • 5xx — Server error
Error response objects conform to RFC 9457 (Problem Details for HTTP APIs). Each error is distinguished by a type attribute and follows a consistent shape.