Claude Agent Sdk Python

Claude Agent SDK Python

Build production-ready agent applications with the Claude Agent SDK for Python.

Quick Reference

Installation

pip install claude-agent-sdk

Requires Python 3.10+ and bundled Claude CLI v2.0.60+.

Core APIs

Basic Patterns

One-Shot Query

import anyio
from claude_agent_sdk import query, AssistantMessage, TextBlock, ResultMessage

async def main():
    async for msg in query(prompt="Explain Python decorators"):
        if isinstance(msg, AssistantMessage):
            for block in msg.content:
                if isinstance(block, TextBlock):
                    print(block.text)
        elif isinstance(msg, ResultMessage):
            print(f"Cost: ${msg.total_cost_usd:.4f}")

anyio.run(main)

Interactive Client

import anyio
from claude_agent_sdk import (
    ClaudeSDKClient,
    ClaudeAgentOptions,
    AssistantMessage,
    TextBlock,
    ResultMessage,
)

async def main():
    options = ClaudeAgentOptions(
        system_prompt="You are a helpful assistant",
        allowed_tools=["Read", "Write", "Bash"],
        permission_mode="acceptEdits",
        max_turns=10,
    )

    async with ClaudeSDKClient(options=options) as client:
        await client.query("Analyze main.py")

        async for msg in client.receive_response():
            if isinstance(msg, AssistantMessage):
                for block in msg.content:
                    if isinstance(block, TextBlock):
                        print(block.text)
            elif isinstance(msg, ResultMessage):
                print(f"Done. Cost: ${msg.total_cost_usd:.4f}")

anyio.run(main)

Custom Tools

from typing import Any
from claude_agent_sdk import tool, create_sdk_mcp_server, ClaudeAgentOptions

@tool("add", "Add two numbers", {"a": float, "b": float})
async def add(args: dict[str, Any]) -> dict[str, Any]:
    result = args["a"] + args["b"]
    return {"content": [{"type": "text", "text": f"Result: {result}"}]}

@tool("divide", "Divide two numbers", {"a": float, "b": float})
async def divide(args: dict[str, Any]) -> dict[str, Any]:
    if args["b"] == 0:
        return {
            "content": [{"type": "text", "text": "Error: Division by zero"}],
            "is_error": True
        }
    return {"content": [{"type": "text", "text": f"Result: {args['a'] / args['b']}"}]}

calculator = create_sdk_mcp_server(
    name="calculator",
    version="1.0.0",
    tools=[add, divide]
)

options = ClaudeAgentOptions(
    mcp_servers={"calc": calculator},
    allowed_tools=["mcp__calc__add", "mcp__calc__divide"],
    permission_mode="acceptEdits",
)

Configuration Reference

ClaudeAgentOptions

ClaudeAgentOptions(
    # Model
    model="claude-sonnet-4-20250514",
    fallback_model=None,

    # Prompts
    system_prompt="You are a helpful assistant",

    # Limits
    max_turns=10,
    max_budget_usd=1.00,
    max_thinking_tokens=8000,

    # Environment
    cwd="/path/to/project",
    env={"CUSTOM_VAR": "value"},

    # Tools
    tools=["Read", "Write", "Bash"],  # or {"type": "preset", "preset": "claude_code"}
    allowed_tools=["Read", "Write"],  # whitelist
    disallowed_tools=["WebFetch"],    # blacklist
    mcp_servers={"name": config},     # custom tools

    # Permissions
    permission_mode="acceptEdits",  # default, acceptEdits, plan, bypassPermissions
    can_use_tool=my_permission_callback,

    # Sessions
    continue_conversation=False,
    resume="session-id",
    fork_session=False,

    # Hooks
    hooks={"PreToolUse": [HookMatcher(matcher="*", hooks=[my_hook])]},
)

Permission Modes

Advanced Patterns

For detailed examples of:

• Permission callbacks: See references/permissions.md
• Lifecycle hooks: See references/hooks.md
• Testing patterns: See references/testing.md
• Production patterns: See references/production.md

Independent App Testing

Use scripts/run_agent_app.py to test agent applications in isolation:

# Run a simple agent app
python scripts/run_agent_app.py path/to/app.py

# Run with custom options
python scripts/run_agent_app.py path/to/app.py --cwd /project --max-turns 5

Use scripts/create_agent_project.py to scaffold new agent projects:

# Create a basic agent project
python scripts/create_agent_project.py my_agent --template basic

# Create with custom tools
python scripts/create_agent_project.py my_agent --template custom-tools

# Create interactive chat app
python scripts/create_agent_project.py my_agent --template chat

Message Types

Content Blocks

from claude_agent_sdk import TextBlock, ThinkingBlock, ToolUseBlock, ToolResultBlock

# In AssistantMessage.content
for block in msg.content:
    if isinstance(block, TextBlock):
        print(block.text)
    elif isinstance(block, ThinkingBlock):
        print(f"Thinking: {block.thinking}")
    elif isinstance(block, ToolUseBlock):
        print(f"Tool: {block.name}, Input: {block.input}")

Error Handling

from claude_agent_sdk import (
    ClaudeSDKError,
    CLINotFoundError,
    ProcessError,
    SDKJSONDecodeError,
)

try:
    async with ClaudeSDKClient(options) as client:
        await client.query("Do something")
        async for msg in client.receive_response():
            process(msg)
except CLINotFoundError:
    print("Claude CLI not found. Install from https://claude.ai")
except ProcessError as e:
    print(f"CLI failed with exit code: {e.exit_code}")
except SDKJSONDecodeError:
    print("Failed to parse CLI response")

Best Practices

1. Always use context managers for ClaudeSDKClient to ensure cleanup
2. Set max_budget_usd to prevent runaway costs
3. Use permission_mode="acceptEdits" for file operations without prompts
4. Return is_error: True from custom tools on failure
5. Use structured outputs for predictable JSON responses
6. Test tools independently before integrating with full agent

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