Messages Count Tokens

Overview

Use POST /api/v1/messages/count_tokens to estimate the number of input tokens for an Anthropic Messages-format request. This endpoint is useful for request planning, context budgeting, and cost control. The result is an estimate and may not exactly match a provider tokenizer.

Endpoint

POST https://nano-gpt.com/api/v1/messages/count_tokens

Authentication

Use either header:

Authorization: Bearer YOUR_API_KEY
x-api-key: YOUR_API_KEY

Request Body

{
  "model": "claude-3-5-sonnet",
  "system": "You are concise.",
  "messages": [
    {
      "role": "user",
      "content": "Hello"
    }
  ],
  "tools": [],
  "tool_choice": null
}

Supported Content

The request uses Anthropic message format and supports:

text blocks
image and document-like blocks
tool use blocks
tool result blocks
system
tools
tool_choice

Response

{
  "input_tokens": 123
}

Example

curl -X POST https://nano-gpt.com/api/v1/messages/count_tokens \
  -H "Authorization: Bearer $NANOGPT_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "claude-3-5-sonnet",
    "system": "You are concise.",
    "messages": [
      { "role": "user", "content": "Hello" }
    ]
  }'

Notes

This is an estimate for planning and cost control.
It may not exactly match a provider tokenizer.
For generation, use POST /api/v1/messages.

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Overview

Endpoint

Authentication

Request Body

Supported Content

Response

Example

Notes

​Overview

​Endpoint

​Authentication

​Request Body

​Supported Content

​Response

​Example

​Notes

Overview

Endpoint

Authentication

Request Body

Supported Content

Response

Example

Notes