# Count tokens for a message

> POST /v1/messages/count_tokens on BigModel.io counts the input tokens of an Anthropic Messages request without generating a reply. Anthropic groups only.

Web version: https://bigmodel.io/docs/api-count-tokens · Updated 2026-10-18

`POST https://bigmodel.io/v1/messages/count_tokens`

Counts the input tokens an Anthropic Messages body would use, without generating a reply and without recording usage. Only Anthropic groups support it; OpenAI groups and chat-only groups (DeepSeek, GLM platforms) return `404`.

## Request

```http
POST https://bigmodel.io/v1/messages/count_tokens
```

### Authentication

| Header | Value |
|---|---|
| `Authorization` | `Bearer $BIGMODEL_API_KEY` |
| `x-api-key` | `$BIGMODEL_API_KEY` |

Send one of these.

### Body

An Anthropic Messages body; `max_tokens` is not needed.

| Field | Type | Required | Description |
|---|---|---|---|
| `model` | string | Yes | Model ID. |
| `messages` | array<object> | Yes | The messages to count. |
| `system` | string \| array<object> |  |  |
| `tools` | array<object> |  |  |

## Response

| Status | Meaning |
|---|---|
| `200` | Token count, as returned by the upstream. |
| `400` | `api_key_in_query_deprecated` (key sent in the query string), or `invalid_request_error`: empty or invalid JSON, missing `model`, a non-boolean `stream`, or another malformed field. |
| `401` | `API_KEY_REQUIRED`, `INVALID_API_KEY`, `API_KEY_DISABLED`, `USER_NOT_FOUND`, `USER_INACTIVE`. |
| `403` | `INSUFFICIENT_BALANCE`, `API_KEY_EXPIRED`, `ACCESS_DENIED` (IP rule), `SUBSCRIPTION_NOT_FOUND`, `SUBSCRIPTION_INVALID`, or a `permission_error` (key without a group, endpoint not allowed for the group). |
| `404` | Token counting is not supported for this key group. |
| `413` | Request body too large. |
| `429` | `API_KEY_QUOTA_EXHAUSTED`, `USAGE_LIMIT_EXCEEDED` (plan limit), or `rate_limit_exceeded` / `rate_limit_error` (key 5h/1d/7d limit, requests per minute, concurrency, upstream). RPM limits send `Retry-After`. |
| `503` | `api_error` and similar: no capacity for this model in your group right now, or the model is not served by your group (`No available accounts`). |

### Response fields

| Field | Type | Description |
|---|---|---|
| `input_tokens` | integer | Input tokens the request would use. |


## Examples

```bash [cURL]
curl https://bigmodel.io/v1/messages/count_tokens \
  -H "Authorization: Bearer $BIGMODEL_API_KEY" \
  -H "anthropic-version: 2023-06-01" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "glm-5.3",
    "system": "You are a concise assistant.",
    "messages": [{"role": "user", "content": "Explain HTTP 429 in one sentence."}]
  }'
```

```python [Python]
import os
from anthropic import Anthropic

client = Anthropic(base_url="https://bigmodel.io", api_key=os.environ["BIGMODEL_API_KEY"])

count = client.messages.count_tokens(
    model="glm-5.3",
    system="You are a concise assistant.",
    messages=[{"role": "user", "content": "Explain HTTP 429 in one sentence."}],
)
print(count.input_tokens)
```

```js [Node.js]
import Anthropic from '@anthropic-ai/sdk'

const client = new Anthropic({baseURL: 'https://bigmodel.io', apiKey: process.env.BIGMODEL_API_KEY})

const count = await client.messages.countTokens({
  model: 'glm-5.3',
  system: 'You are a concise assistant.',
  messages: [{role: 'user', content: 'Explain HTTP 429 in one sentence.'}],
})
console.log(count.input_tokens)
```

Example response (the count is illustrative):

```json
{"input_tokens": 21}
```

## Notes

- **Not available on every group.** OpenAI groups and chat-only groups return `404` with `{"type":"error","error":{"type":"not_found_error","message":"Token counting is not supported for this platform"}}`. For those groups, read `usage` from the actual response instead.
- **The count comes from the upstream**, so it reflects that model's tokenizer.
- **Billing checks still apply.** Counting is not charged, but like other text endpoints it needs a positive balance or an active plan (`403` `INSUFFICIENT_BALANCE` otherwise).
- An empty or invalid body returns `400` `invalid_request_error`; an oversized one `413`. Full list: [Errors](https://bigmodel.io/docs/errors).

## Related

- [Create a message](https://bigmodel.io/docs/api-messages)
- [Billing & top-ups](https://bigmodel.io/docs/billing)