> ## Documentation Index
> Fetch the complete documentation index at: https://docs.stateset.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Add a new belief

> **Required scope:** write

**Required scope:** `write`

### Request body

`AddBeliefRequest`

<ParamField body="confidence" type="number (float)" required>
  Initial confidence (0.0 to 1.0)
</ParamField>

<ParamField body="proposition" type="string" required>
  The proposition (belief statement)
</ParamField>

<ParamField body="source" type="string">
  Source of the belief
</ParamField>

### Response

`BeliefResponse`

<ResponseField name="belief_interval" type="object[]" required />

<ResponseField name="confidence" type="number (float)" required />

<ResponseField name="is_certain" type="boolean" required />

<ResponseField name="is_rejected" type="boolean" required />

<ResponseField name="proposition" type="string" required />

<ResponseField name="uncertainty" type="number (float)" required />

### Status codes

| Code  | Meaning                                            |
| ----- | -------------------------------------------------- |
| `201` | Belief added                                       |
| `400` | Invalid belief                                     |
| `401` | Unauthorized — missing or invalid credentials      |
| `403` | Forbidden — the key/token lacks the required scope |
| `429` | Rate limited — see Retry-After / X-RateLimit-Reset |

<RequestExample>
  ```bash cURL theme={null}
  curl --request POST \
    --url 'https://api.nsr.stateset.com/api/v1/beliefs' \
    --header 'X-API-Key: YOUR_API_KEY' \
    --header 'Content-Type: application/json' \
    --data '{
    "confidence": 0.95,
    "proposition": "socrates_is_mortal",
    "source": "observation"
  }'
  ```
</RequestExample>

<ResponseExample>
  ```json 201 theme={null}
  {
    "belief_interval": [
      {}
    ],
    "confidence": 7.5,
    "is_certain": true,
    "is_rejected": true,
    "proposition": "string",
    "uncertainty": 1.5
  }
  ```
</ResponseExample>