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Anthropic are building a series of Large Language Models under the name Claude. In this example we show how to use their approach to function calls and tools (currenly in Beta).

The tool function definitions and execution of the API calls for the selected tool(s) is handled by Superface using the Hub API endpoints. The choice of which tool to use, and other decision making is handled by Claude.

You can download this example as a runnable .ipynb notebook.


The Anthropic Python SDK is required for this example.

pip install anthropic


Import the dependencies and configure the required constants. Some of these, such as those relating to the SUPERFACE_USER_ID are for example purposes. In a production environment you would handle this differenly, as outlined in the Session Management guide.

import anthropic
import json
import requests as r
from IPython.display import display, Markdown

# Set a random number of your choice, but don't change it
# once you have run the notebook, otherwise you will create another user.

# Use the number to create a unique ID

# Default URL for Superface

# Set the Superface authentication token

# Set the OpenAI API Key

Anthropic Setup

To initialize the Anthropic SDK, pass in your API key.

client = anthropic.Anthropic(api_key=ANTHROPIC_API_KEY)

Helper functions

There are a lot of repetitive tasks when dealing with LLMs so having some helper functions to cut down on code is always the way to go. First we define two functions to use with Superface's Hub API.

# Helper function to return the tool function descriptors
def get_superface_tools():
headers = {"Authorization": "Bearer "+ SUPERFACE_AUTH_TOKEN}
tools = r.get(SUPERFACE_BASE_URL + "/fd", headers=headers)
return tools.json()

# Helper function to perform the action for all the functions.
# This is the only API call required regardless of what the function is.
def perform_action(tool_name=None, tool_body=None):
headers = {"Authorization": "Bearer "+ SUPERFACE_AUTH_TOKEN, "x-superface-user-id": SUPERFACE_USER_ID}
perform = + "/perform/" + tool_name, headers=headers, json=tool_body)
return json.dumps(perform.json())

The first function, get_superface_tools(), retrieves the function descriptions for any tools that have been added in your Superface account. At the very least, you'll already have the tool that this example uses.

The second function, perform_action(), is responsible for executing the API request for the tool and specific function that Claude will choose. It also ensures that this request is authenticated as a specific user using the x-superface-user-id header.

Transform function descriptions

The JSON schema for defining tools that Anthropic requires is slightly different to that used by OpenAI, MistraAI and LangChain. To account for this, the helper function below reformats the JSON response from get_superface_tools().

def get_formatted_tools():
original_tools = get_superface_tools()
formatted_tools = []

for tool in original_tools:

for tool in formatted_tools:
tool['input_schema'] = tool.pop("parameters")

return formatted_tools

The final helper is to communicate with Claude. This is also where the model selection, initial system prompt, list of tools and message history are set up.

def talk_to_claude(role=None, message=None):
messages.append({"role": role, "content": message})
response =
system="Today is April 5, 2024",
return response

Message history

This example needs a "memory" of all the interactions between the user, the API and Claude. An array is a good way to do this:

messages = []


Next, set up the initial user prompt. Asking about the weather is the most simplistic example you can do but it's also the example that Anthropic use for their function calling documentation so we've mirrored that here to help you compare.

response = talk_to_claude("user", "What's the weather like in Prague?")

What is Claude thinking?

Claude likes to think. The first response to a user prompt will contain what Claude thinks the best approach is for obtaining the result. It can vary slightly depending on the amount of inputs a tool expects.

To get the current weather forecast for Prague, I should use the weather__current-weather__CurrentWeather function. Let's check if I have the required parameters:

city: The user provided "Prague" as the city. To be more precise, I'll specify "Prague, Czech Republic".
units: This is an optional parameter. The user did not specify units, so I can omit this and the function will use the default of Celsius.

I have the required city parameter, so I can proceed with calling the function.

Additionally, as part of the response Claude will provide the name of the selected tool, and the required inputs so that a call to the Superface Hub API can be made.

Perform function call

If Claude wants to use a tool (which is this case is true), add the last response to the message history, then extract the function name, and the inputs and use the perform_action() helper to pass them to the Hub API.

if (response.content[1] and response.content[1].type == "tool_use"):
claude_response = response.content[1]
"role": "assistant",
"content": [
"type": "text",
"text": response.content[0].text
"type": claude_response.type,
"input": claude_response.input

function_name =
function_inputs = claude_response.input
tool_use_id =

superface_response = perform_action(function_name, function_inputs)


The response from Superface in this instance will look similar to this:

"status": "success",
"assistant_hint": "Format the result in 'result' field to the user. If the user asked for a specific format, respect it",
"result": {
"description": "Partly cloudy",
"feelsLike": 16,
"temperature": 16

Final response

Now that the Hub API has executed the function and returned a result, this needs to be added to the message history and sent back to Claude to determine a final response.

tool_response_content = [{
"type": "tool_result",
"tool_use_id": tool_use_id,
"content": superface_response

claude_response = talk_to_claude("user", tool_response_content)

Claude will reply with the final response which can also be added to the message history:

messages.append({"role": "assistant", "content": claude_response.content[0].text})

In notebook form, this can be displayed nicely to the user:

Current weather in Prague, Czech Republic: Temperature: 16°C Feels like: 16°C Description: Partly cloudy


This example builds on the function calling example that Anthropic use, however, with Superface's Hub API you can access many varied APIs, including your own custom tools.

The approach to implementing those would be similar, especialy when you consider that just a single function is required to execute any of the functions an LLM selects and Superface will handle it from there.

For more information on how to implement function calling with Anthropic Claude3, take a look at their documentation.