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This provider supports the Anthropic Claude series of models.


To use Anthropic, you need to set the ANTHROPIC_API_KEY environment variable or specify the apiKey in the provider configuration.

Create Anthropic API keys here.

Example of setting the environment variable:

export ANTHROPIC_API_KEY=your_api_key_here

Supported Parameters

Config PropertyEnvironment VariableDescription
apiKeyANTHROPIC_API_KEYYour API key from Anthropic
apiBaseUrlANTHROPIC_BASE_URLThe base URL for requests to the Anthropic API

Latest API (Messages)

The messages API supports all the latest Anthropic models.

The anthropic provider supports the following models via the messages API:

  • anthropic:messages:claude-3-5-sonnet-20240620
  • anthropic:messages:claude-3-haiku-20240307
  • anthropic:messages:claude-3-sonnet-20240229
  • anthropic:messages:claude-3-opus-20240229
  • anthropic:messages:claude-2.0
  • anthropic:messages:claude-2.1
  • anthropic:messages:claude-instant-1.2

Prompt Template

To allow for compatibility with the OpenAI prompt template, the following format is supported:

Example: prompt.json

"role": "system",
"content": "{{ system_message }}"
"role": "user",
"content": "{{ question }}"

If the role system is specified, it will be automatically added to the API request. All user or assistant roles will be automatically converted into the right format for the API request. Currently, only type text is supported.

The system_message and question are example variables that can be set with the var directive.


The Anthropic provider supports several options to customize the behavior of the model. These include:

  • temperature: Controls the randomness of the output.
  • max_tokens: The maximum length of the generated text.
  • top_p: Controls nucleus sampling, affecting the randomness of the output.
  • top_k: Only sample from the top K options for each subsequent token.
  • tools: An array of tool or function definitions for the model to call.
  • tool_choice: An object specifying the tool to call.

Example configuration with options and prompts:

- id: anthropic:messages:claude-3-opus-20240229
temperature: 0.0
max_tokens: 512
prompts: [prompt.json]

Tool Use

The Anthropic provider supports tool use (or function calling). Here's an example configuration for defining tools:

- id: anthropic:messages:claude-3-opus-20240229
- name: get_weather
description: Get the current weather in a given location
type: object
type: string
description: The city and state, e.g., San Francisco, CA
type: string
- celsius
- fahrenheit
- location

See the Anthropic Tool Use Guide for more information on how to define tools and the tool use example here.

Images / Vision

You can include images in the prompts in Claude 3 models.

See the Claude vision example.

One important note: The Claude API only supports base64 representations of images. This is different from how OpenAI's vision works, as it supports grabbing images from a URL. As a result, if you are trying to compare Claude 3 and OpenAI vision capabilities, you will need to have separate prompts for each.

See the OpenAI vision example to understand the differences.

Additional Capabilities

  • Caching: Caches previous LLM requests by default.
  • Token Usage Tracking: Provides detailed information on the number of tokens used in each request, aiding in usage monitoring and optimization.
  • Cost Calculation: Calculates the cost of each request based on the number of tokens generated and the specific model used.

Deprecated API (Completions)

The completions API is deprecated. See the migration guide here.

The anthropic provider supports the following models:

  • anthropic:completion:claude-1
  • anthropic:completion:claude-1-100k
  • anthropic:completion:claude-instant-1
  • anthropic:completion:claude-instant-1-100k
  • anthropic:completion:<insert any other supported model name here>

Supported environment variables:

  • ANTHROPIC_API_KEY - required
  • ANTHROPIC_STOP - stopwords, must be a valid JSON string
  • ANTHROPIC_MAX_TOKENS - maximum number of tokens to sample, defaults to 1024

Config parameters may also be passed like this:

- id: anthropic:completion:claude-1
prompts: chat_prompt
temperature: 0

Model-Graded Tests

Model-graded assertions such as factuality or llm-rubric use OpenAI by default and expect OPENAI_API_KEY as an environment variable. If you are using Anthropic, you may override the grader to point to a different provider.

Because of how model-graded evals are implemented, the model must support chat-formatted prompts (except for embedding or classification models).

The easiest way to do this for all your test cases is to add the defaultTest property to your config:

id: anthropic:messages:claude-3-opus-20240229
# Provider config options

However, you can also do this for individual assertions:

# ...
- type: llm-rubric
value: Do not mention that you are an AI or chat assistant
id: anthropic:messages:claude-3-opus-20240229
# Provider config options

Or individual tests:

# ...
- vars:
# ...
id: anthropic:messages:claude-3-opus-20240229
# Provider config options
- type: llm-rubric
value: Do not mention that you are an AI or chat assistant