get_num_tokens_from_messages

from langchain_anthropic import ChatAnthropic
from langchain_core.messages import HumanMessage, SystemMessage

model = ChatAnthropic(model="claude-sonnet-4-5-20250929")

messages = [
    SystemMessage(content="You are a scientist"),
    HumanMessage(content="Hello, Claude"),
]
model.get_num_tokens_from_messages(messages)

14

from langchain_anthropic import ChatAnthropic
from langchain_core.messages import HumanMessage
from langchain_core.tools import tool

model = ChatAnthropic(model="claude-sonnet-4-5-20250929")

@tool(parse_docstring=True)
def get_weather(location: str) -> str:
    """Get the current weather in a given location

    Args:
        location: The city and state, e.g. San Francisco, CA
    """
    return "Sunny"

messages = [
    HumanMessage(content="What's the weather like in San Francisco?"),
]
model.get_num_tokens_from_messages(messages, tools=[get_weather])

403