The outcome

Implement a useful agent loop without giving the model broader access or ambiguity than the task requires.

LangChain is a open-source framework for building model- and tool-using agents. Building agents with standardized model interfaces, typed tools, structured output, middleware, persistence, and human approval controls. This guide narrows that broad capability into one repeatable outcome, with checkpoints that keep the source material and your judgment in the loop.

Before you begin

Set the boundary before the tool starts.

Choose one real task, identify who will use the result, and decide what evidence or test will make the result acceptable. Gather only the source material needed for that task. If the work contains confidential, personal, regulated, or client-owned information, confirm that the platform and account are approved before sharing it.

Troiana principle

AI should make the work easier to inspect. If the workflow removes the source, the owner, or the review step, redesign the workflow.

Step by step

A workflow you can repeat.

  1. 01

    Write the task contract, accepted inputs, output schema, success criteria, iteration limit, and actions that require approval.

  2. 02

    Choose a supported model and define the minimum tools with narrow typed arguments, clear descriptions, validated returns, and timeouts.

  3. 03

    Create the agent with an explicit system prompt and structured response schema, keeping credentials and authorization inside tool code.

  4. 04

    Run normal, ambiguous, adversarial, tool-error, repeated-call, and malformed-output cases while recording the complete execution trace.

  5. 05

    Add middleware for retries, limits, redaction, and human review, then pin dependencies and version the test set before release.

Working standard

What good use looks like.

  • Expose the fewest possible tools.
  • Validate every tool boundary.
  • Bound agent iterations and cost.

Framework abstractions do not make model choices or tools safe. Validate every tool boundary, limit iterations and cost, protect credentials, isolate user state, trace behavior, and require approval for consequential actions.

Official references

Check the current product documentation.

Features, plan limits, availability, and data controls change. These official pages are the starting points used for this collection.