Claude API Getting Started: From the First Message to Reliable Long-Context Work

The first Claude integration trap

Do not interpret a large context window as permission to dump unlimited material into a request. Long-context work still needs chunking, deduplication, citations, and access control. A model can read a document without every sentence being true or applicable.

A sensible integration order

Start with one short Messages API request, add a system instruction, test a long-document summary, and only then add tool use. At every step record input size, latency, and human edit rate.

System versus user

Use system instructions for stable role, principles, and boundaries. Use the user message for the current task and materials. Changing prices, policies, and inventory belong in controlled context retrieved from business systems, not in a permanent system prompt.

Long-document checkpoints

Split documents into titled sections, ask the model to cite section names or excerpts, sample-check summaries, and require rule plus human approval before any output triggers fulfillment, refunds, or quotes.

Tool boundaries

Tools should be narrow-permission functions such as checking an order or inventory. Never give a model a universal arbitrary-code entry point by default. Validate arguments, user permissions, and side effects on the server.

Official source: Anthropic Claude API Getting Started. Follow Anthropic's current documentation for SDKs, model names, and safety guidance.