For the complete documentation index, see llms.txt. Markdown versions of all docs pages are available by appending .md to any docs URL.

Token count

Count tokens through agentgateway using the Anthropic Messages token-count API.

The Anthropic token-count API (/v1/messages/count_tokens) estimates the number of input tokens in an Anthropic Messages request before sending it to a model.

About

Agentgateway supports the Anthropic Messages token-count endpoint with the anthropicTokenCount route type. Use this endpoint when clients need to estimate request size before calling /v1/messages, such as to enforce budgets, avoid context-window limits, or show usage estimates.

Route type configuration

In the simplified llm configuration, agentgateway automatically maps /v1/messages/count_tokens requests to the anthropicTokenCount route type, so no explicit route configuration is required.

# yaml-language-server: $schema=https://agentgateway.dev/schema/config
llm:
  models:
  - name: "*"
    provider: anthropic
    params:
      apiKey: "$ANTHROPIC_API_KEY"

To configure the route type explicitly, use the binds/listeners/routes format and set the anthropicTokenCount route type in the policies.ai.routes map. Most configurations also map /v1/messages to the messages route type for the actual model request.

# yaml-language-server: $schema=https://agentgateway.dev/schema/config
binds:
- port: 4000
  listeners:
  - routes:
    - backends:
      - ai:
          name: anthropic
          provider:
            anthropic: {}
      policies:
        ai:
          routes:
            "/v1/messages": "messages"
            "/v1/messages/count_tokens": "anthropicTokenCount"
        backendAuth:
          key: "$ANTHROPIC_API_KEY"

Using the API

Send a request to the /v1/messages/count_tokens endpoint with the same message shape that you would send to /v1/messages.

curl 'http://localhost:4000/v1/messages/count_tokens' \
--header 'Content-Type: application/json' \
--data '{
  "model": "claude-opus-4-6",
  "messages": [
    {
      "role": "user",
      "content": "How many tokens are in this request?"
    }
  ]
}'

For Anthropic-specific features such as Messages, token counting, extended thinking, and structured outputs, see the Anthropic provider guide.