anthropic

@composio/anthropic

Adapts Composio tools to the Claude Messages API and executes the tool calls Claude returns.

Installation

npm install @composio/core @composio/anthropic @anthropic-ai/sdk

Set COMPOSIO_API_KEY (create one at https://dashboard.composio.dev/settings) and ANTHROPIC_API_KEY (from https://console.anthropic.com/settings/keys) in your environment.

Quickstart

Create a session for your user, pass its tools to the Messages API, and run the tool-call loop until Claude replies with text. handleToolCalls executes every tool_use block and returns a ready-to-append user message of tool_result blocks.

import Anthropic from '@anthropic-ai/sdk';
import { Composio } from '@composio/core';
import { AnthropicProvider } from '@composio/anthropic';

const composio = new Composio({
  provider: new AnthropicProvider(),
});
const client = new Anthropic();

// Create a session for your user
const session = await composio.create('user_123');
const tools = await session.tools();

const messages: Anthropic.MessageParam[] = [
  {
    role: 'user',
    content:
      "Send an email to john@example.com with the subject 'Hello' and body 'Hello from Composio!'",
  },
];

let response = await client.messages.create({
  model: 'claude-opus-4-6',
  max_tokens: 4096,
  tools,
  messages,
});

// Agentic loop: keep executing tool calls until the model responds with text
while (response.stop_reason === 'tool_use') {
  const toolResults = await composio.provider.handleToolCalls(session, response);
  messages.push({ role: 'assistant', content: response.content });
  messages.push(...toolResults);
  response = await client.messages.create({
    model: 'claude-opus-4-6',
    max_tokens: 4096,
    tools,
    messages,
  });
}

// Print final response
for (const block of response.content) {
  if (block.type === 'text') {
    console.log(block.text);
  }
}

Building on the Claude Agent SDK instead? Use @composio/claude-agent-sdk, which exposes Composio tools as an in-process MCP server and lets the SDK run the loop.

Provider options

• cacheTools: pass new AnthropicProvider({ cacheTools: true }) to attach Anthropic's ephemeral cache_control to every tool definition and tool-result block. This lets Claude reuse cached tool schemas across requests and can cut prompt cost when you send the same large tool set on every turn. It is the only constructor option.
• handleToolCalls(session, message) returns Anthropic.Messages.MessageParam[], not raw strings, so you append the result directly to your message list. Pass a user ID instead of a session for tools fetched with tools.get(). For finer control, executeToolCall(session, toolUseBlock) runs a single tool_use block and returns the result as a JSON string.
• Claude occasionally emits a tool's input as a JSON string instead of an object; the provider normalizes this before execution.

Links

• Anthropic provider docs
• Composio documentation