Company Logo
About usContact Us
Recommended Reading
Integrating Large Language Models with External Tools: A Practical Guide to API Function Calls

AI

Integrating Large Language Models with External Tools: A Practical Guide to API Function Calls

August 22, 2025 · 10 min read

Introduction

In this tutorial we explore how we can connect OpenAI’s Chat Completions API to external services through function calling. This capability allows the model to generate JSON objects that can serve as instructions to call external functions based on user inputs.
AI gives you superpowers, it’s no longer just for chatting. Now, it can take real-world actions like sending emails, fetching live data, or updating databases. Explore how to set up structured functions, validate parameters, and handle responses to build dynamic AI applications that do more than just respond. Get ready to turn your chatbot into an active problem-solver that seamlessly connects with your entire tech setup. 

Understanding Function Calling in the Chat Completions API

The Chat completion API provides us with an optional parameter “tools” that we can use to provide function definitions. The LLM will then select function arguments which match the provided function specifications.
One important thing to understand is that OpenAI doesn’t call any function. It simply returns the function definition, and the developer can then execute that function.
1. Optional “Tool” Parameter:
2. LLM Function Selection:
3. No Automatic Function Execution:
4. Developer Responsibility:

Common Use Cases

The completion response is computed and after that it is returned.
1. Make calls to external APIs: Use tools to make calls to external api. Build agents that can understand and perform external tasks by defining functions. For example: generating user location or fetching pending tasks for this week:
get_pending_tasks(type: ‘week|month|quarter’)
get_current_location() 
send_friend_request(userId) · 

2. Connect to SQL Database: Using Natural language, define functions that can make request to database queries.
get_data_from_db(query)

How It Works

Integrating LLMs with external tools involves a few straightforward steps:  
1. Define Functions:
Define Functions
Define-Functions-1536x1513.webp
2. Call the Model:
Call-the-Model.webp

3. Handle the Output:
The JSON output from the model will contain the necessary details to call the external function. This may include function names and argument values.
Handle-the-Output-1536x397.webp

If a tool was called, the “finish_reason“ in the ocmpletion respnse will be equal to “tool_calls“. Also, there will be a “tool_calls” object that will contain the name of tool as well as any arguments.
4. Execute Functions:
Execute-Functions-1536x254.webp

5. Process and Respond:
After executing the function, you might need to call the model again with the results to generate a user-friendly summary or further instructions.
Execute-Functions-1536x254 (1).webp

Conclusion

Integrating OpenAI’s Chat Completions API with external tools improves the functional capabilities of applications. By defining functions and utilizing the ‘tool’ parameter, developers can create interactions that use real-time data and actions to increase the responsiveness and versatility of their software.
Ready to improve your business operations by innovating Data into conversations? Click here to see how Data Outlook can help you automate your processes.

Have a Question?

puneet Taneja

Puneet Taneja

CPO (Chief Planning Officer)

Table of Contents

Have a Question?

puneet Taneja

Puneet Taneja

CPO (Chief Planning Officer)

Frequently Asked Questions

Yes, using function calling, ChatGPT can suggest calling external tools like APIs, databases, or webhooks. However, execution happens on the developer’s end, not within the model itself.

By defining functions inside the tools parameter during API calls, developers allow the model to generate arguments. Once received, developers process and execute the function logic externally.

Common examples include sending emails, pulling real-time weather or stock data, querying SQL databases, or managing user workflows like to-do lists and reminders.

No. OpenAI only generates a structured function call. Execution and validation are done manually or through the developer’s backend.

Related Articles

Is Investing in AI Consulting Services Worth in 2025?
AI
Is Investing in AI Consulting Services Worth in 2025?

Discover how AI consulting services are helping businesses reshape strategy, automate operations, and stay ahead in 2025’s data-driven economy.

Read more about Is Investing in AI Consulting Services Worth in 2025?

12 Customized AI Hacks to Keep Your Business Ahead in 2025
AI
12 Customized AI Hacks to Keep Your Business Ahead in 2025

Explore 12 customized AI hacks to keep your business competitive in 2025. Use customized AI solutions for automation, decision-making, and customer retention.

Read more about 12 Customized AI Hacks to Keep Your Business Ahead in 2025

How Automation Solved 90% of Payment Reconciliation Problems
AI
How Automation Solved 90% of Payment Reconciliation Problems

Tired of messy payment reconciliations? How an e-commerce seller can solve it with smart automation without any manual uploads, just smooth, error-free syncs.

Read more about How Automation Solved 90% of Payment Reconciliation Problems

Contact

Us

Trusted By

trusted brand
trusted brand
trusted brand
trusted brand
trusted brand
trusted brand
trusted brand
trusted brand
trusted brand
trusted brand
trusted brand
trusted brand
trusted brand
trusted brand
trusted brand
trusted brand
trusted brand
trusted brand
Complere logo

Complere Infosystem is a multinational technology support company that serves as the trusted technology partner for our clients. We are working with some of the most advanced and independent tech companies in the world.

Award 1Award 2Award 3Award 4
Award 1Award 2Award 3Award 4

Contact Info

For Career+91 9518894544
For Inquiries+91 9991280394
D-190, 4th Floor, Phase- 8B, Industrial Area, Sector 74, Sahibzada Ajit Singh Nagar, Punjab 140308
1st Floor, Kailash Complex, Mahesh Nagar, Ambala Cantt, Haryana 133001
Opening Hours: 8.30 AM – 7.00 PM
Subscribe to our newsletter

Privacy Policy

Terms & Conditions

Career

Cookies Preferences

© 2025 Complere Infosystem – Data Analytics, Engineering, and Cloud Computing Powered by Complere Infosystem