Skip to main content
POST
/
v1
/
messages
/
count_tokens
Count Tokens
curl --request POST \
  --url https://openp.ai/v1/messages/count_tokens
import requests

url = "https://openp.ai/v1/messages/count_tokens"

response = requests.post(url)

print(response.text)
const options = {method: 'POST'};

fetch('https://openp.ai/v1/messages/count_tokens', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));
<?php

$curl = curl_init();

curl_setopt_array($curl, [
  CURLOPT_URL => "https://openp.ai/v1/messages/count_tokens",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "POST",
]);

$response = curl_exec($curl);
$err = curl_error($curl);

curl_close($curl);

if ($err) {
  echo "cURL Error #:" . $err;
} else {
  echo $response;
}
package main

import (
	"fmt"
	"net/http"
	"io"
)

func main() {

	url := "https://openp.ai/v1/messages/count_tokens"

	req, _ := http.NewRequest("POST", url, nil)

	res, _ := http.DefaultClient.Do(req)

	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)

	fmt.Println(string(body))

}
HttpResponse<String> response = Unirest.post("https://openp.ai/v1/messages/count_tokens")
  .asString();
require 'uri'
require 'net/http'

url = URI("https://openp.ai/v1/messages/count_tokens")

http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true

request = Net::HTTP::Post.new(url)

response = http.request(request)
puts response.read_body
Estimate the token count before actually calling /v1/messages, useful for:
  • Checking in advance whether you’ll exceed the context window.
  • Precisely estimating cost in batch jobs.
  • Showing the token count on the client.

Request

curl https://openp.ai/v1/messages/count_tokens \
  -H "x-api-key: $OPENPAI_API_KEY" \
  -H "anthropic-version: 2023-06-01" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "claude-opus-4-8",
    "messages": [{"role": "user", "content": "hello"}]
  }'
The fields are the same as /v1/messages (can include system / tools / messages), and you don’t need to provide generation parameters like max_tokens.

Response

{ "input_tokens": 9 }

Billing

The count_tokens endpoint doesn’t consume model quota, but it is still subject to the OpenPAI gateway’s RPM rate limiting.