Claude Agent SDK for Python
Python SDK for Claude Agent. See the Claude Agent SDK documentation for more information.
Installation
pip install claude-agent-sdk
Prerequisites:
- Python 3.10+
Note: The Claude Code CLI is automatically bundled with the package - no separate installation required! The SDK will use the bundled CLI by default. If you prefer to use a system-wide installation or a specific version, you can:
- Install Claude Code separately:
curl -fsSL https://claude.ai/install.sh | bash - Specify a custom path:
ClaudeAgentOptions(cli_path="/path/to/claude")
Quick Start
import anyio from claude_agent_sdk import query async def main(): async for message in query(prompt="What is 2 + 2?"): print(message) anyio.run(main)
Basic Usage: query()
query() is an async function for querying Claude Code. It returns an AsyncIterator of response messages. See src/claude_agent_sdk/query.py.
from claude_agent_sdk import query, ClaudeAgentOptions, AssistantMessage, TextBlock # Simple query async for message in query(prompt="Hello Claude"): if isinstance(message, AssistantMessage): for block in message.content: if isinstance(block, TextBlock): print(block.text) # With options options = ClaudeAgentOptions( system_prompt="You are a helpful assistant", max_turns=1 ) async for message in query(prompt="Tell me a joke", options=options): print(message)
Using Tools
options = ClaudeAgentOptions( allowed_tools=["Read", "Write", "Bash"], permission_mode='acceptEdits' # auto-accept file edits ) async for message in query( prompt="Create a hello.py file", options=options ): # Process tool use and results pass
Working Directory
from pathlib import Path options = ClaudeAgentOptions( cwd="/path/to/project" # or Path("/path/to/project") )
ClaudeSDKClient
ClaudeSDKClient supports bidirectional, interactive conversations with Claude
Code. See src/claude_agent_sdk/client.py.
Unlike query(), ClaudeSDKClient additionally enables custom tools and hooks, both of which can be defined as Python functions.
Custom Tools (as In-Process SDK MCP Servers)
A custom tool is a Python function that you can offer to Claude, for Claude to invoke as needed.
Custom tools are implemented in-process MCP servers that run directly within your Python application, eliminating the need for separate processes that regular MCP servers require.
For an end-to-end example, see MCP Calculator.
Creating a Simple Tool
from claude_agent_sdk import tool, create_sdk_mcp_server, ClaudeAgentOptions, ClaudeSDKClient # Define a tool using the @tool decorator @tool("greet", "Greet a user", {"name": str}) async def greet_user(args): return { "content": [ {"type": "text", "text": f"Hello, {args['name']}!"} ] } # Create an SDK MCP server server = create_sdk_mcp_server( name="my-tools", version="1.0.0", tools=[greet_user] ) # Use it with Claude options = ClaudeAgentOptions( mcp_servers={"tools": server}, allowed_tools=["mcp__tools__greet"] ) async with ClaudeSDKClient(options=options) as client: await client.query("Greet Alice") # Extract and print response async for msg in client.receive_response(): print(msg)
Benefits Over External MCP Servers
- No subprocess management - Runs in the same process as your application
- Better performance - No IPC overhead for tool calls
- Simpler deployment - Single Python process instead of multiple
- Easier debugging - All code runs in the same process
- Type safety - Direct Python function calls with type hints
Migration from External Servers
# BEFORE: External MCP server (separate process) options = ClaudeAgentOptions( mcp_servers={ "calculator": { "type": "stdio", "command": "python", "args": ["-m", "calculator_server"] } } ) # AFTER: SDK MCP server (in-process) from my_tools import add, subtract # Your tool functions calculator = create_sdk_mcp_server( name="calculator", tools=[add, subtract] ) options = ClaudeAgentOptions( mcp_servers={"calculator": calculator} )
Mixed Server Support
You can use both SDK and external MCP servers together:
options = ClaudeAgentOptions( mcp_servers={ "internal": sdk_server, # In-process SDK server "external": { # External subprocess server "type": "stdio", "command": "external-server" } } )
Hooks
A hook is a Python function that the Claude Code application (not Claude) invokes at specific points of the Claude agent loop. Hooks can provide deterministic processing and automated feedback for Claude. Read more in Claude Code Hooks Reference.
For more examples, see examples/hooks.py.
Example
from claude_agent_sdk import ClaudeAgentOptions, ClaudeSDKClient, HookMatcher async def check_bash_command(input_data, tool_use_id, context): tool_name = input_data["tool_name"] tool_input = input_data["tool_input"] if tool_name != "Bash": return {} command = tool_input.get("command", "") block_patterns = ["foo.sh"] for pattern in block_patterns: if pattern in command: return { "hookSpecificOutput": { "hookEventName": "PreToolUse", "permissionDecision": "deny", "permissionDecisionReason": f"Command contains invalid pattern: {pattern}", } } return {} options = ClaudeAgentOptions( allowed_tools=["Bash"], hooks={ "PreToolUse": [ HookMatcher(matcher="Bash", hooks=[check_bash_command]), ], } ) async with ClaudeSDKClient(options=options) as client: # Test 1: Command with forbidden pattern (will be blocked) await client.query("Run the bash command: ./foo.sh --help") async for msg in client.receive_response(): print(msg) print("\n" + "=" * 50 + "\n") # Test 2: Safe command that should work await client.query("Run the bash command: echo 'Hello from hooks example!'") async for msg in client.receive_response(): print(msg)
Types
See src/claude_agent_sdk/types.py for complete type definitions:
ClaudeAgentOptions- Configuration optionsAssistantMessage,UserMessage,SystemMessage,ResultMessage- Message typesTextBlock,ToolUseBlock,ToolResultBlock- Content blocks
Error Handling
from claude_agent_sdk import ( ClaudeSDKError, # Base error CLINotFoundError, # Claude Code not installed CLIConnectionError, # Connection issues ProcessError, # Process failed CLIJSONDecodeError, # JSON parsing issues ) try: async for message in query(prompt="Hello"): pass except CLINotFoundError: print("Please install Claude Code") except ProcessError as e: print(f"Process failed with exit code: {e.exit_code}") except CLIJSONDecodeError as e: print(f"Failed to parse response: {e}")
See src/claude_agent_sdk/_errors.py for all error types.
Available Tools
See the Claude Code documentation for a complete list of available tools.
Examples
See examples/quick_start.py for a complete working example.
See examples/streaming_mode.py for comprehensive examples involving ClaudeSDKClient. You can even run interactive examples in IPython from examples/streaming_mode_ipython.py.
Migrating from Claude Code SDK
If you're upgrading from the Claude Code SDK (versions < 0.1.0), please see the CHANGELOG.md for details on breaking changes and new features, including:
ClaudeCodeOptions→ClaudeAgentOptionsrename- Merged system prompt configuration
- Settings isolation and explicit control
- New programmatic subagents and session forking features
Development
If you're contributing to this project, run the initial setup script to install git hooks:
./scripts/initial-setup.sh
This installs a pre-push hook that runs lint checks before pushing, matching the CI workflow. To skip the hook temporarily, use git push --no-verify.
Building Wheels Locally
To build wheels with the bundled Claude Code CLI:
# Install build dependencies pip install build twine # Build wheel with bundled CLI python scripts/build_wheel.py # Build with specific version python scripts/build_wheel.py --version 0.1.4 # Build with specific CLI version python scripts/build_wheel.py --cli-version 2.0.0 # Clean bundled CLI after building python scripts/build_wheel.py --clean # Skip CLI download (use existing) python scripts/build_wheel.py --skip-download
The build script:
- Downloads Claude Code CLI for your platform
- Bundles it in the wheel
- Builds both wheel and source distribution
- Checks the package with twine
See python scripts/build_wheel.py --help for all options.
Release Workflow
The package is published to PyPI via the GitHub Actions workflow in .github/workflows/publish.yml. To create a new release:
-
Trigger the workflow manually from the Actions tab with two inputs:
version: The package version to publish (e.g.,0.1.5)claude_code_version: The Claude Code CLI version to bundle (e.g.,2.0.0orlatest)
-
The workflow will:
- Build platform-specific wheels for macOS, Linux, and Windows
- Bundle the specified Claude Code CLI version in each wheel
- Build a source distribution
- Publish all artifacts to PyPI
- Create a release branch with version updates
- Open a PR to main with:
- Updated
pyproject.tomlversion - Updated
src/claude_agent_sdk/_version.py - Updated
src/claude_agent_sdk/_cli_version.pywith bundled CLI version - Auto-generated
CHANGELOG.mdentry
- Updated
-
Review and merge the release PR to update main with the new version information
The workflow tracks both the package version and the bundled CLI version separately, allowing you to release a new package version with an updated CLI without code changes.
License and terms
Use of this SDK is governed by Anthropic's Commercial Terms of Service, including when you use it to power products and services that you make available to your own customers and end users, except to the extent a specific component or dependency is covered by a different license as indicated in that component's LICENSE file.