Richard Mendes
March 20, 2026 • 5 minsOpen your AWS Lambda function, go to index.js, and paste the following code:
export const handler = async (event) => {
try {
const apiKey = process.env.API_KEY;
// Parse the incoming request body
const body = JSON.parse(event.body || "{}");
const text = body.text || "paid for groceries";
// Construct the prompt dynamically
const prompt = `
Convert the following sentence into a two-word financial description.
Examples:
paid for groceries -> Groceries Payment
paid the rent -> Rent Expense
got rent income -> Rent Income
Sentence: ${text}
Return exactly two words.
`;
// Call Gemini API
const response = await fetch(
"https://generativelanguage.googleapis.com/v1beta/models/gemini-3-flash-preview:generateContent",
{
method: "POST",
headers: {
"Content-Type": "application/json",
"x-goog-api-key": apiKey,
},
body: JSON.stringify({
contents: [{ parts: [{ text: prompt }] }],
}),
}
);
const data = await response.json();
console.log("Full API response:", data);
// Extract the two-word result safely
let result = "Unknown ";
if (data.candidates && data.candidates[0].content) {
const content = data.candidates[0].content;
if (content.parts && content.parts[0] && content.parts[0].text) {
const textResult = content.parts[0].text.trim();
if (textResult.split(/\s+/).length === 2) result = textResult;
} else if (content.text) {
const textResult = content.text.trim();
if (textResult.split(/\s+/).length === 2) result = textResult;
}
}
// Return proper JSON
return {
statusCode: 200,
headers: { "Content-Type": "application/json" },
body: JSON.stringify({ description: result }),
};
} catch (error) {
console.error("Error calling Gemini API:", error);
return {
statusCode: 500,
body: JSON.stringify({ error: error.message }),
};
}
};
Example Request. Send a POST request with JSON body like this:
{
"text": "paid for groceries"
}
Example Response
{
"description": "Groceries Payment"
}
This function works with API Gateway and requires an API key (see video for full setup).
https://youtu.be/oWfugLxJs5U