Understand Claude messages, content, and completion

Define the conversation you are sending

Give a request a clear task and the context needed to complete it. For a documentation explanation, include the approved reference excerpt and the user’s question. Keep application-level instructions separate from quoted material so their purpose is clear.

The Messages API documentation describes structured conversation content and how clients supply history for stateless multi-turn requests. Decide which prior messages are relevant and how your application preserves important decisions as a conversation grows.

Inspect the whole response

Claude’s stop-reason documentation identifies why a response stopped, including completed turns, output limits, tool use, and refusals. Your client should handle the applicable reasons for the endpoint and model it uses. A returned message is not automatically a complete answer to the user’s task.

• Content: Read the documented content structure rather than assuming every item is plain text.
• Completion: Distinguish a finished answer from a request for further tool processing.
• Validation: Check required output fields and whether claims are supported by input evidence.
• Recovery: Preserve context when the response is incomplete or cannot be used.

For tool-assisted work, separate the model’s requested action from the application’s execution result. The application must validate arguments, enforce permissions, and supply the appropriate result before the conversation can continue meaningfully.

Test the task, then refine it

Begin with representative examples and a known output requirement. Add a case with missing information, a case with contradictory source text, and a case that requires the response to stay within a defined scope. Review whether the result is useful and properly qualified.

Check the current documentation when selecting a model or enabling an optional parameter. Record the model, endpoint, prompt, and schema together so a later change can be compared with the earlier behavior.

Keep a short failure taxonomy: insufficient evidence, incorrect interpretation, incomplete generation, and application parsing failure. Each category points toward a different corrective action.

The Anthropic provider guide covers access and operations. Continue to LLM prompt contracts when Claude output feeds another application component.