The Claude API enables developers to build sophisticated applications with tool use, vision, and structured outputs.

Tool Use (Function Calling)

Claude can use tools you define to interact with external systems:

import anthropic

client = anthropic.Anthropic()

tools = [{
    "name": "search_database",
    "description": "Search the product database",
    "input_schema": {
        "type": "object",
        "properties": {
            "query": {"type": "string"},
            "category": {"type": "string", "enum": ["electronics", "clothing", "home"]}
        },
        "required": ["query"]
    }
}]

response = client.messages.create(
    model="claude-sonnet-4-20250514",
    max_tokens=1024,
    tools=tools,
    messages=[{"role": "user", "content": "Find me wireless headphones under $100"}]
)

Computer Use

Claude can interact with computer interfaces — clicking, typing, scrolling, and reading screens:

• Automate repetitive desktop tasks
• Test web applications by navigating them
• Fill out forms and process documents
• Navigate complex software interfaces

Vision

Send images to Claude for analysis:

• Screenshots for debugging
• Documents and receipts for data extraction
• Charts and graphs for interpretation
• Product images for descriptions

Prompt Caching

Cache frequently used system prompts and documents:

response = client.messages.create(
    model="claude-sonnet-4-20250514",
    system=[{
        "type": "text",
        "text": long_system_prompt,
        "cache_control": {"type": "ephemeral"}
    }],
    messages=[{"role": "user", "content": "Analyze this contract"}]
)

Caching reduces costs by 90% and latency by 85% for repeated prompts.