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Building Reliable Applications with LLM APIs

Build an application that uses a language model and stays reliable when the model is wrong, slow or unavailable. You build Larkfield's ticket assistant step by step, from one request to validated answers, safe tools and tested failure paths.

Read every lesson as a guest, or sign in to enroll and track your progress.

What you'll learn

By the end of this course, you will be able to:

  • Integrate an LLM behind a clear application interface.
  • Design and evaluate prompts and structured outputs.
  • Execute tools through validated application code.
  • Handle streaming, failures and usage budgets.

About this course

A language model can read a support ticket and draft a good reply in seconds. Putting that into an application is a different job. The model sometimes returns text that your code cannot read, invents an order number, asks a tool for something it should not see, or does not answer at all because the provider is busy.

In this course, you build an application that expects all of this. You start with one request and read every part of it. Then you turn prompts into specifications that you can test, turn answers into validated data, and let the model ask for tools while your code keeps control of what runs.

Larkfield’s help desk gives you one assistant for the whole course: it routes each ticket to a team, says whether a person must check it, drafts a reply and can look up an order. By the end, it retries safely, logs what every call costs, and passes tests for every failure path you have seen.

You do not need an account or a paid key. Every lesson runs with recorded responses from real models, and you can switch to a free local model or your own key at any point. Diagrams and annotated outputs carry the main ideas, so the text stays short.

Before you start

You completed Python for Practical AI Engineering and LLMs, How They Work and How to Choose One, or you have the same skills. You do not need an API key or a paid account. Every lesson runs with recorded responses, and you can use a free local model or your own key if you want live calls.

Courses to take first: Python for Practical AI Engineering, LLMs: How They Work and How to Choose One.

Who this is for

People who can write Python and know what a language model does, as in LLMs, How They Work and How to Choose One, and want to build a real application on a model API. Developers, data scientists and professionals moving into AI engineering.

How we made this course

Experienced AI practitioners designed this course. AI helped us draft the content; people chose the teaching approach and the examples, and reviewed every lesson. The outputs that you see are the actual results of running the code. How we make our courses

Inside the course

Module 2Prompting as an engineering task

3 lessons

Treat a prompt as a specification. Write the task, its audience, limits and output contract; mark untrusted customer text clearly; and compare prompt versions on a fixed set of tickets instead of one good answer.

  1. Specify the task50 min
  2. Provide context safely50 min
  3. Compare prompts50 min

Module 3Structured outputs and validation

3 lessons

Make the model's output data you can trust. Define a schema, handle refusals, cut-off and malformed answers, and check the meaning, because valid JSON can still be wrong.

  1. Define a schema50 min
  2. Handle incomplete results45 min
  3. Validate meaning45 min

Module 4Tool calling safely

3 lessons

Let the model ask for tools, and let your code decide. Describe a read-only tool, check every argument and permission before it runs, and stop loops that repeat or run too long.

  1. Describe a tool50 min
  2. Execute in application code50 min
  3. Bound the loop45 min

Final module · choose at least oneCase studies

3 case studies

Three end-to-end case studies on open data. Extract product recalls into structured records, answer questions with read-only tools, and classify banking requests and compare an LLM with a fine-tuned model. Complete at least one for the certificate; each one is a portfolio piece.

Complete at least one case study for the certificate. The others are optional. What each one covers

  1. Extract product recalls into structured data180 min
  2. Answer questions with tools over open data180 min
  3. Classify banking requests with an LLM120 min

After the case studiesFinal assignment

Use every module in one practice project. You collect evidence, and check it against the course outcomes.

  1. Final assignment300 min

Case studies

Realistic projects from start to finish, on real data, with every output explained. Each one makes a portfolio piece. Complete at least one for the certificate; the others are optional.

  1. Extract product recalls into structured data3 hr

    Turn public product-recall notices into validated structured records with a schema, business checks and a measured error rate on a hand-checked sample.

  2. Answer questions with tools over open data3 hr

    Build an assistant that answers questions about an open dataset only through validated, read-only tools, with a bounded loop and checked numbers.

  3. Classify banking requests with an LLM2 hr

    Classify customer banking requests with prompts and structured output, compare prompt versions on a fixed set, and compare accuracy and cost with a fine-tuned small model.

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