# Authenticate your backend

```
POST 
/oauth/token
```

Use this endpoint to get a medium-lived JWT access token for your backend to perform calls the Server API exposed by Nabla. See the [Authentication](/guides/authentication.md) guide for details on how to construct the client assertion.

## Request[​](#request "Direct link to request")

## Responses[​](#responses "Direct link to Responses")

* 200

A JWT access token that can be used to access the server API.

## Operation spec

```json
{
  "method": "post",
  "path": "/oauth/token",
  "operationId": "oauth-generate-server-access-token",
  "requestBody": {
    "required": true,
    "content": {
      "application/json": {
        "schema": {
          "type": "object",
          "properties": {
            "grant_type": {
              "type": "string",
              "description": "This endpoint only supports the 'client_credentials' value.",
              "example": "client_credentials"
            },
            "client_assertion_type": {
              "type": "string",
              "description": "This endpoint only supports the 'urn:ietf:params:oauth:client-assertion-type:jwt-bearer' value.",
              "example": "urn:ietf:params:oauth:client-assertion-type:jwt-bearer"
            },
            "client_assertion": {
              "type": "string",
              "description": "A short-lived JWT assertion that serves to authenticate this request."
            }
          },
          "required": [
            "grant_type",
            "client_assertion_type",
            "client_assertion"
          ]
        }
      }
    }
  },
  "responses": {
    "200": {
      "description": "A JWT access token that can be used to access the server API.",
      "content": {
        "application/json": {
          "schema": {
            "type": "object",
            "properties": {
              "access_token": {
                "type": "string",
                "description": "An authentication token using the JWT serialization format. JWT tokens contain varying data (depending on their intended use) and use a signature to guarantee their authenticity.",
                "example": "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJ0eXBlIjoiYWNjZXNzIiwic3ViIjoiMTIzNDU2Nzg5MCIsIm5hbWUiOiJKb2huIERvZSIsImlhdCI6MTUxNjIzOTAyMn0.v5qdy8w9Ygs5fdic9a1LuX76PUdx3omYd5GlDTAF3Ug",
                "title": "jwt_token"
              },
              "expires_in": {
                "type": "integer",
                "description": "The lifetime of the access token, in seconds."
              }
            },
            "required": [
              "access_token",
              "expires_in"
            ]
          }
        }
      }
    }
  }
}
```