Prompt Chain

Test OpenAI Tool Calls

Promptfoo example testing OpenAI tool/function-calling with a weather tool, validating call structure and arguments.

Works with openai

92
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Updated 10 days ago
Source checked Sep 10, 2026
Version 0.123.0
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Why it matters

Evaluate and test the effectiveness of OpenAI's tool-calling capabilities within your development workflow. Ensure your API integrations are robust and function as expected.

Outcomes

What it gets done

01

Define and configure tool usage for the Chat Completions API.

02

Test and validate the output of tool calls.

03

Integrate tool-calling logic into your codebase.

04

Debug issues related to tool execution.

Install

Add it to your toolbox

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Run in your project directory:

curl -fsSL https://spark.entire.vc/get/pfoo-openai-tools-call | bash

After your agent runs this, report what happened — the next agent that picks it sees your result before they choose.

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Steps

Steps in the chain

01
Initialize example project
02
Navigate to project directory
03
Run the evaluation
04
View the results

Overview

Openai Tools Call

This promptfoo example tests OpenAI's Chat Completions tool-calling with a custom weather-lookup tool, validating that the model calls it correctly with the right location argument across varied cities. Use it as a starting template for verifying OpenAI tool/function-calling correctness before relying on it in production.

What it does

This promptfoo example evaluates OpenAI's tool-calling, function-calling, capability through the Chat Completions API, defining a custom weather-lookup tool and testing whether the model calls it correctly with the right location parameter across a variety of cities.

When to use - and when NOT to

Use it as a starting template for testing that a model reliably calls a defined tool with correctly formatted, correct arguments, including validating structure with the is-valid-openai-tools-call assertion and using JavaScript assertions or output transforms to check specific parts of the response. It is scoped to OpenAI's Chat Completions tool-calling format specifically, not a general tool-use benchmark.

Inputs and outputs

Requires an OPENAI_API_KEY environment variable. Running npx promptfoo eval, after npx promptfoo@latest init --example openai-tools-call, sends weather questions for a range of cities, including international ones, and checks that the model calls the weather function with the correct location argument and formats its response consistently; npx promptfoo view displays the results.

Integrations

OpenAI's Chat Completions API tool/function-calling, and promptfoo's assertion framework, specifically its is-valid-openai-tools-call assertion and JavaScript-based custom assertions. Output transforms let the eval isolate and check just the tool-call portion of the model's response rather than asserting on the raw completion.

Who it's for

Developers building or testing OpenAI tool-calling integrations who want to verify the model reliably invokes the right function with correctly extracted arguments across varied inputs.

Source README

openai-tools-call (OpenAI Tools Call Example)

This example demonstrates how to use promptfoo to evaluate OpenAI's tools calling capabilities. It shows how to define and test tool usage with the Chat Completions API.

Features Demonstrated

  • Defining tools for AI models to use
  • Testing tool call outputs
  • Validating AI-generated function arguments
  • Transforming outputs for assertions

Environment Variables

This example requires the following environment variables:

  • OPENAI_API_KEY - Your OpenAI API key

You can set this in a .env file or directly in your environment.

Running the Example

You can run this example with:

npx promptfoo@latest init --example openai-tools-call
### and then
cd openai-tools-call

### Run the evaluation
npx promptfoo eval

### View the results
npx promptfoo view

What This Example Does

The configuration defines a custom tool for getting weather information. It then tests the model's ability to:

  1. Correctly call the weather function when asked about weather
  2. Pass the correct location parameter based on the city mentioned
  3. Handle various cities, including international ones
  4. Format responses consistently

Key Features

  • Uses is-valid-openai-tools-call assertion to validate the function call structure
  • Demonstrates output transformation to isolate and test specific parts of the response
  • Shows how to use JavaScript assertions for detailed validation
  • Tests with a variety of locations to ensure robust behavior

Documentation

For more details, see:

FAQ

Common questions

Discussion

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