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How to Build a CRM with Replit AI Agent: A Step-by-Step Guide

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Author: Ram Bansal
Ram Bansal
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Introduction

AI-powered coding tools are rapidly transforming how developers build software, shifting development from manual coding to a more automated process. These IDEs (Integrated Development Environments) come with AI assistants that can generate code, suggest fixes, and even configure projects based on natural language prompts. 

Imagine launching a fully functional Customer Relations Management (CRM) in days, not months—here’s how AI makes it possible. In this series of blog posts, we’ll use AI Coding Agents and Nylas APIs to build a CRM faster than traditional methods, integrating email, contacts, and scheduling effortlessly. 

This guide is perfect for developers, startups, or small teams looking to streamline customer management. In this blog post, we are going to get started with Replit AI Agent—an AI-powered coding assistant integrated into Replit—and Nylas communication APIs, you’ll see how to scaffold a practical CRM system in record time. Let’s jump in!

Why Build a CRM with AI?

Building a CRM from scratch traditionally involves time-consuming tasks like manually syncing emails and calendars across different provider APIs, slowing down development. AI-powered IDEs, like Replit AI Agent, simplify this by generating integration code from natural language prompts, while Nylas APIs unify these connections, speeding up the process. Here’s why this approach stands out:

  • Cut development time with AI-generated code: Automate repetitive tasks and boilerplate.
  • Unify email, contacts, and calendars with Nylas APIs: Seamless integrations without the hassle.
  • Focus on features, not boilerplate: Let AI and Nylas handle the heavy lifting.

This lets you prototype core CRM features quickly, with the AI acting as a pair programmer to reduce errors and focus on business logic. Want more details? See how Nylas simplifies CRM development in just three sprints. 

Ready to see it in action? Let’s set up Replit and get started.

Getting Started with Replit AI Agent

To kick off our project, let’s jump into our development environment. Follow these steps to get started:

1. Set Up Replit: Sign up for Replit to access the Replit Agent.

2. Create a New Project: When you sign up for Replit, you are presented with a prompt input. In the prompt UI shared, note the functionality to attach files and also improve your initial prompt:

We will circle back to entering a prompt shortly where we initialize a new project for creating a CRM using Nylas starter prompts.

3. Configure Nylas API Credentials: Sign up for a free Nylas developer account and obtain your API keys. The Replit Agent will help you set up environment variables securely. As part of building with Replit, you will be prompted to enter specific credentials as we build a CRM. You’ll need to create a API Key and note the Client ID from the Nylas Dashboard:

Important: never commit secrets to source control.

4. AI-Assisted Workflow: Now you are ready for the fun part! In the upcoming sections, we will provide ready-made prompts to get us building a basic CRM that you can extend with additional functionality.

Replit Agent will generate code or guide you through the setup. Embrace an iterative workflow: you provide instructions in natural language, and the AI writes or modifies code accordingly. This interactive development will be used in the next sections to implement CRM functionality. With the environment ready and the AI pair-programmer at your side, we can move on to integrating the core CRM functionality.

Note on tech stack: We will be building using Node.js and React. You can choose a tech stack you’re comfortable with – for example, a Node.js/Express app (for a JavaScript backend) or a Python/Flask app.

Leveraging Nylas APIs for CRM Functionality

A CRM typically needs to handle emails, contacts, and calendar events. Instead of writing separate integrations for Gmail, Outlook, etc., we use Nylas APIs to get universal access to all providers. Here’s a quick overview of Nylas API capabilities and how each fits into our CRM:

Nylas APICRM FeatureBenefits
Email APISending and reading emailsAllow users to view threads and send emails. Unified inbox for all providers.
Contacts APISyncs a contact list from the user’s email providerCentralize customer and lead management
Calendar APICreate and retrieve events.Supporting scheduling for meetings and follow-ups with two-way sync across calendars.
CRM features overview

Nylas provides comprehensive docs and even AI prompt guides to help integrate these APIs (AI prompts quickstart guide: Use AI prompts with Nylas). As we implement each feature, we’ll reference relevant Nylas documentation and use prompts designed for those APIs.

In the next section, we’ll build the CRM features step by step, using Replit Agent to generate most of the code and Nylas to handle the heavy lifting for communications features.

Building CRM Functionality

Now we’ll develop the main features of our CRM. For each feature, we’ll explain the approach along with links to any useful resources. You can literally instruct the AI with these requirements, and it will produce similar code. We’ll focus on:

  1. User Authentication using Nylas Hosted Authentication
  2. Email Integration using Nylas Email API
  3. Contact Management using Nylas Contact API
  4. Calendar Scheduling using Nylas Calendar and Events API

(Optional) CRM Product Requirement Document

This is totally optional, but it’s useful to work with an LLM model to generate a basic product requirement document (PRD) for the features you are looking to build. This is a good practice to give an idea of what you are looking to build out with the aim to build out each feature step by step via prompting (i.e. few-shot prompting). Here is a sample CRM description that we can use as part of our initial prompts to Replit Agent:

# Nylas-Powered CRM MVP

## 1. Overview

**Product Name:** Nylas-Powered CRM MVP
### Purpose
This document defines the **Minimum Viable Product (MVP)** for a Customer Relationship Management (CRM) system integrating Gmail email provider via Nylas API V3 (Email, Calendar, Contacts). Built with **Node.js**, and **React**It leverages the Nylas Node.js SDK V3 (reference: https://nylas-nodejs-sdk-reference.pages.dev) for a single-user prototype, generated in one shot using Replit’s AI coding tool. It outlines features, authentication, and technical setup for a small sales team.

### Goals & Objectives
1. **Demonstrate Core Functionality**: Show how Nylas APIs can enable seamless email, contact, and calendar integration.
2. **Build a Minimal but Usable CRM**: Provide essential workflows for a small sales team (3–5 members) within a 10–15 person company.
---
## 2. Target Users
1. **Sales Reps** (3–5 team members): Need an integrated inbox, contact management, and a way to schedule meetings.
2. **Sales Manager / Admin**: Sets up the application, manages team accounts, and configures the Nylas authentication.
---
## 3. Key Features
### 3.1 Onboarding & Authentication (Nylas OAuth)
**Objective**: Securely integrate one sales rep’s email account using Nylas Hosted Authentication.
---
### 3.2 Email Integration
**Objective**: Display the sales rep’s recent Gmail emails in a unified inbox.
---
### 3.3 Contact Management
**Objective**: Provide a single source of truth for leads/contacts.
---
## 4. Technical Requirements
1. **Nylas OAuth Flow** (Node.js):
   - Implement the redirect flow for each user’s mailbox.
   - Securely store grant IDs.
2. **Backend**:
   - Use **Node.js** + Express or similar.
   - Integrate the official Nylas Node SDK to call Email, Contacts, Calendar APIs.
3. **Frontend**:
   - Implement a UI for inbox, contact list, event calendar, and user onboarding.
4. **Database**:
   - Store user profiles, Nylas grant IDs, contact references, and event info.
   - Consider using in-memory storage to start
---
## Conclusion
This PRD specifies a Node.js prototype for the Nylas-Powered CRM MVP. By integrating the official Nylas Node SDK for Email, Contacts, and Calendar, we can rapidly deliver essential features (unified inbox, contact management, and calendar events) while providing a foundation for more advanced capabilities.

User Authentication (OAuth with Nylas)  

First, we need to authenticate the user and connect their email account to our app. We’ll use Nylas Hosted OAuth for a simplified login flow. Nylas hosted authentication is the quickest way to set up user auth for email/calendar providers – you redirect users to a Nylas login page, and Nylas handles the rest (including provider detection and token exchange).

In practice, you’ll create an OAuth URL and have the user authorize your application. Nylas will return a grant ID (in Nylas API v3) for the connected account, which we’ll use in subsequent API calls. Replit Agent can help generate the auth route. Let’s get started with our first prompt to the Replit Agent:

View attached starter prompts: 
1) A starter prompt to build with Nylas APIs, 
2) A PRD for a CRM that I like to build using the Nylas API, and 
3) A prompt to explain how to build hosted authentication.

Since the CRM requires a lot of integrations, I want to start step by step and build and test things out as I go. So build features and I will manually test them sequentially. Let's start with adding Nylas Hosted Authentication to connect to user's accounts.

Here is a screen shot of the initial prompt:

I pasted the following prompts:

Before clicking Start building consider using the improve prompt feature on Replit to get a revised prompt:

A web-based CRM system with Nylas API integration, starting with the implementation of Nylas Hosted Authentication as the first phase to enable user account connections.

Core Features:
- Implement Nylas Hosted Authentication flow
- Enable users to securely connect their email accounts
- Handle authentication callbacks and token management
- Display connection status for authenticated accounts

Visual References:
Inspired by Hubspot and Salesforce's authentication flows, known for their clear and secure authentication processes.

Style Guide:
- Colors: Primary #00B6B0 (Nylas teal), Secondary #2D2E83 (deep blue), Background #FFFFFF (white), Text #333333 (dark grey), Accent #FF6B6B (coral)
- Design: Inter/SF Pro Display fonts, clean authentication interface, clear call-to-action buttons, progress indicators, responsive layout with 16px spacing

It should produce code to generate the auth URL and a callback endpoint to capture the authorization code and exchange it for credentials. During this step, you may be stopped to enter specific environment variables:



Resource: Nylas OAuth Guide – This explains setting up Hosted Auth and the redirect flow. Consider reviewing our authentication guides if you happen to get stuck, as it will be the most challenging step for a coding agent to get right on the first try.

After this step, you will have the ability to authenticate a user and retrieve a Nylas grantId associated with the user. Now the CRM can use Nylas APIs on behalf of that user. For a quick start, you could also hardcode a grant ID from your own test account while prototyping.

Here is a short code snippet of the code Replit produced:

// Initialize Nylas with API key
const nylas = new Nylas({
  apiKey: process.env.NYLAS_API_KEY!,
});

// Generate auth URL for connecting Google
app.get("/api/auth/nylas", async (req, res) => {
  const authUrl = nylas.auth.urlForOAuth2({
    clientId: process.env.NYLAS_CLIENT_ID!,
    redirectUri: process.env.NYLAS_REDIRECT_URI!,
    provider: "google",
    scope: ["openid", "https://www.googleapis.com/auth/gmail.modify", /* more scopes... */],
  });
  res.json({ authUrl });
});

// Handle OAuth callback
app.get("/api/nylas/callback", async (req, res) => {
  const { code } = req.query;
  const tokenResponse = await nylas.auth.exchangeCodeForToken({
    clientId: process.env.NYLAS_CLIENT_ID!,
    clientSecret: process.env.NYLAS_API_KEY!,
    code: code as string,
    redirectUri: process.env.NYLAS_REDIRECT_URI!,
  });
  
  // Store user with grant ID for API access
  await storage.createUser({
    username: "demo",
    grantId: tokenResponse.grantId,
    emailConnected: tokenResponse.email
  });
  
  res.redirect("/?success=true");
});

The below example application was generated by Replit (UI may vary):

Email Integration (Using Nylas Email API)

With authentication in place, we can integrate email functionality. The goal here is to allow the CRM to retrieve and send emails through the user’s email account, all via the Nylas Email API. This lets a sales rep see their conversation with a contact or send a follow-up email without switching to an external email client.

Using the Replit Agent, we can generate an email module quickly using the email feature prompt. Paste the email feature prompt in the prompt input and add the following:

I like to consider adding the next steps, so I have received a prompt from Nylas to use. I like to add Email functionality using the Nylas APIs. View attached prompt.

This will allow the Replit Agent to have the sufficient context to build the Nylas Email API integration and build out a UI to read and send emails. The AI Agent will handle the boilerplate for error catching and response. You now have email sending and reading integrated with minimal manual coding. Make sure to adjust email scopes during OAuth to allow sending email if you implement this.

Here is a short code snippet of the code Replit produced:

// Fetch emails from user's mailbox
app.get('/api/nylas/emails', async (req, res) => {
  try {
    const user = await storage.getUserByUsername("demo");
    if (!user?.grantId) return res.status(401).json({ error: "User not connected" });
    
    const { limit = 10, cursor } = req.query;
    const queryParams = { limit: Number(limit) };
    if (cursor) queryParams.cursor = cursor;
    
    const messages = await nylas.messages.list({
      identifier: user.grantId,
      queryParams
    });
    
    res.json(messages);
  } catch (error) {
    res.status(500).json({ error: "Failed to fetch emails" });
  }
});

// Send an email
app.post('/api/nylas/emails/send', async (req, res) => {
  try {
    const user = await storage.getUserByUsername("demo");
    if (!user?.grantId) return res.status(401).json({ error: "User not connected" });
    
    const { to, subject, body } = req.body;
    if (!to || !subject || !body) return res.status(400).json({ error: "Missing required fields" });
    
    const toRecipients = Array.isArray(to) ? to.map(email => ({ email })) : [{ email: to }];
    
    const sentMessage = await nylas.messages.send({
      identifier: user.grantId,
      requestBody: { to: toRecipients, subject, body }
    });
    
    res.json({ message: "Email sent successfully", data: sentMessage });
  } catch (error) {
    res.status(500).json({ error: "Failed to send email" });
  }
});

The below example application was generated by Replit (UI may vary):

For more advanced email features, check out the Nylas Email API docs – you can list threads, search emails, download attachments, etc., all through similar SDK calls.

Contact Management (Using Nylas Contacts API)

Next, let’s integrate the contacts/address book. Our CRM should be able to display and manage the user’s contacts (customers, leads, etc.). Since the user authenticated their email, we can use that same connection to sync contacts via the Nylas Contacts API.

Using the Replit Agent, we can generate a contact module quickly using the contact feature prompt. Paste the contact feature prompt in the prompt input and add the following:

I like to consider adding the next steps, so I have received a prompt from Nylas to use. I like to add Contacts functionality using the Nylas APIs. View attached prompt.

For adding contacts, Nylas provides an API to create or update a contact. This will allow the Replit Agent to have the sufficient context to build the Nylas Contact API integration and build out a UI to read and create contacts.

Here is a short code snippet of the code Replit produced:

// Fetch contacts
app.get('/api/nylas/contacts', async (req, res) => {
  try {
    const user = await storage.getUserByUsername("demo");
    if (!user?.grantId) return res.status(401).json({ error: "User not connected" });
    
    const { limit = 20, cursor, email } = req.query;
    const queryParams = { limit: Number(limit) };
    if (cursor) queryParams.cursor = cursor;
    if (email) queryParams.email = email;
    
    const contacts = await nylas.contacts.list({
      identifier: user.grantId,
      queryParams
    });
    
    res.json(contacts);
  } catch (error) {
    res.status(500).json({ error: "Failed to fetch contacts" });
  }
});

// Create a new contact
app.post('/api/nylas/contacts', async (req, res) => {
  try {
    const user = await storage.getUserByUsername("demo");
    if (!user?.grantId) return res.status(401).json({ error: "User not connected" });
    
    const { givenName, surname, emails } = req.body;
    if (!givenName || !emails || emails.length === 0) {
      return res.status(400).json({ error: "Missing required fields" });
    }
    
    const newContact = await nylas.contacts.create({
      identifier: user.grantId,
      requestBody: { givenName, surname, emails }
    });
    
    res.status(201).json({
      message: "Contact created successfully",
      data: newContact.data
    });
  } catch (error) {
    res.status(500).json({ error: "Failed to create contact" });
  }
});

You can then display these in a contacts page of your CRM. Because Nylas normalizes the data, it doesn’t matter if the user’s contacts are in Google Contacts, Outlook People, or any other provider – the API returns a consistent JSON format. 

The below example application was generated by Replit (UI may vary):

With a couple of AI-generated routes, your CRM now has a basic contacts module: listing contacts, searching by name, and creating new contacts that sync back to the user’s contacts list.

Calendar Scheduling (Using Nylas Calendar API)  

The final core feature is calendar integration – enabling scheduling of meetings or viewing events. In a CRM, this could mean showing the user’s calendar availability, scheduling a call with a customer, or logging events like follow-up reminders. 

We’ll leverage the Nylas Calendar API for this. Using the Replit Agent, we can generate a calendar module quickly using the calendar events feature prompt. Paste the calendar feature prompt in the prompt input and add the following:

I like to consider adding the next steps, so I have received a prompt from Nylas to use. I like to add Events functionality using the Nylas APIs. View attached prompt.

This will allow the Replit Agent to have the sufficient context to build the Nylas Events API integration and build out a UI to read and create calendar events. This code uses nylas.events.create to add a calendar event for the authenticated user. Nylas handles sending out the invite and syncing the event across all devices. You just specify the details. The AI will likely include error handling and date conversions (remember to use seconds for timestamps as noted in the docs).

Here is a short code snippet of the code Replit produced:

// Fetch calendar events
app.get('/api/nylas/events', async (req, res) => {
  try {
    const user = await storage.getUserByUsername("demo");
    if (!user?.grantId) return res.status(401).json({ error: "User not connected" });
    
    const { start_time, end_time, calendar_id, limit = 10 } = req.query;
    
    const queryParams = {};
    if (start_time) queryParams.starts_after = start_time;
    if (end_time) queryParams.ends_before = end_time;
    if (calendar_id) queryParams.calendar_id = calendar_id;
    queryParams.limit = Number(limit);
    
    const events = await nylas.events.list({
      identifier: user.grantId,
      queryParams
    });
    
    res.json({
      events: events.data,
      next_page_token: events.next_page_token
    });
  } catch (error) {
    res.status(500).json({ error: "Failed to fetch events" });
  }
});

// Create a calendar event
app.post('/api/nylas/events', async (req, res) => {
  try {
    const user = await storage.getUserByUsername("demo");
    if (!user?.grantId) return res.status(401).json({ error: "User not connected" });
    
    const { title, calendar_id, start_time, end_time } = req.body;
    if (!title || !calendar_id || !start_time || !end_time) {
      return res.status(400).json({ error: "Missing required fields" });
    }
    
    const event = await nylas.events.create({
      identifier: user.grantId,
      requestBody: {
        title,
        when: { start_time, end_time }
      },
      queryParams: { calendar_id }
    });
    
    res.status(201).json({
      message: "Event created successfully",
      data: event.data
    });
  } catch (error) {
    res.status(500).json({ error: "Failed to create event" });
  }
});

The below example application was generated by Replit (UI may vary):

If you prefer not to build a scheduling UI from scratch, note that Nylas also offers a pre-built Scheduler widget (a frontend component for booking meetings). You can embed that in your app for a polished scheduling interface with minimal effort.

At this stage, our CRM can authenticate a user, show their emails and contacts, and allow scheduling events – all main pillars of a customer management tool. And thanks to Replit Agent, much of the code was generated from simple instructions, with Nylas APIs and SDK making the integrations trivial.

Build with Nylas  

Now we’ve seen how an AI-powered IDE and Nylas APIs can drastically accelerate building a CRM! Now it’s your turn to take this further. If you haven’t already, sign up for a free Nylas developer account to start building.

Here are some next steps and resources to help you continue:

  • Get Your Free API Key: Visit the Nylas Dashboard and create a new application to obtain your API Key and Client ID
  • AI Prompt quickstart guide: With AI prompts, you can integrate email, calendar, and contacts right away.  
  • Nylas Documentation: Dive into the Nylas Docs for detailed guides, SDK references, and examples.
  • Join the Community: Check out the Nylas developer community.

We encourage you to start your own build – sign up for Nylas, fire up Replit Agent, and let AI speed up development.

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