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How to Build an AI Astrology App in One Weekend: Architecture, APIs, and Cost Breakdown

•
12 min read
•By Sarah Chen
tutorialAI Astrology AppMCPOpenAIClaudeBuild Astrology AppAstrology API TutorialAI Chatbot

Step-by-step guide to building a production-ready AI astrology app in a weekend. Architecture, MCP integration, example endpoints, and real cost estimates for developers.

How to Build an AI Astrology App in One Weekend: Architecture, APIs, and Cost Breakdown

Building an astrology app used to mean months of work. You needed to implement Swiss Ephemeris calculations, build chart rendering, write interpretation logic, handle timezone edge cases, and test against authoritative sources. Most teams gave up halfway through.

In 2026, the entire stack has changed. With the right astrology API and an AI agent framework, you can go from zero to a working AI astrology chatbot in a single weekend. Not a toy demo. A real app that generates birth charts, interprets planetary aspects, draws tarot cards, and answers astrology questions in natural language.

This tutorial walks through the architecture, the API integration, the AI pipeline, and the actual cost of running it in production. By Sunday evening, you will have a working app that your users can talk to.

What You Are Building

A conversational AI astrology assistant that can:

  • Generate complete birth charts with house cusps, planetary positions, and aspects
  • Interpret natal chart placements in plain language
  • Calculate compatibility between two people
  • Provide daily, weekly, and monthly horoscopes
  • Draw tarot cards and explain their meanings
  • Calculate numerology life path numbers
  • Answer follow-up questions using conversation context

The app will use an AI agent (OpenAI, Claude, or Gemini) connected to astrology API endpoints via MCP (Model Context Protocol). Users ask questions in natural language, the AI figures out which API calls to make, and synthesizes the results into a helpful response.

Architecture Overview

Here is the high-level data flow:

User (chat interface)
    |
    v
Your App (Next.js / React / mobile)
    |
    v
AI Agent (OpenAI / Claude / Gemini)
    |
    v  (MCP tool calls)
RoxyAPI (astrology, tarot, numerology endpoints)
    |
    v
AI Agent (synthesizes data into response)
    |
    v
User (sees interpreted reading)

Key insight: The AI agent acts as the intelligence layer between the user and the data API. Users never see raw JSON. They ask "What does my Moon in Scorpio mean?" and get a conversational answer backed by real astronomical calculations.

Component Breakdown

Component Role Technology
Frontend Chat interface Next.js, React Native, or any framework
AI Agent Natural language understanding + tool calling OpenAI Agents SDK, Claude, or Gemini
Data API Astrology calculations, tarot, numerology RoxyAPI (MCP-connected)
Database User profiles, saved readings (optional) Postgres, Supabase, or Firebase

Saturday Morning: Set Up the Foundation

Step 1: Get Your API Key (2 minutes)

Visit roxyapi.com/pricing and grab a Starter plan. Your API key is generated instantly after checkout. No approval process, no waiting.

The Starter plan gives you 5,000 requests/month across all six domains (Western astrology, Vedic astrology, tarot, numerology, dreams, I-Ching). Every request costs the same regardless of endpoint complexity. That is enough for development plus early users.

Step 2: Test the API (5 minutes)

Before writing any code, verify the API works. Generate a natal chart:

curl -X POST "https://roxyapi.com/api/v2/astrology/natal-chart" \
  -H "X-API-Key: YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "date": "1990-06-15",
    "time": "14:30",
    "latitude": 40.7128,
    "longitude": -74.0060,
    "timezone": -4
  }'

You get back a complete birth chart: planetary positions with zodiac signs and degrees, house cusps for all 12 houses, aspects between planets, and interpretation summaries. All in clean JSON.

Try a tarot draw:

curl -X POST "https://roxyapi.com/api/v2/tarot/draw" \
  -H "X-API-Key: YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"count": 3, "allowReversals": true}'

Three cards with names, positions, reversed status, keywords, full meanings, and card artwork URLs.

Step 3: Connect MCP to Your AI Agent (5 minutes)

This is where the magic happens. Instead of writing custom API integration code, you connect the AI agent to RoxyAPI via MCP. The agent automatically discovers all available endpoints and can call them as tools.

For OpenAI Agents SDK (Python):

from agents import Agent, Runner
from agents.mcp import MCPServerSse

# Connect to RoxyAPI MCP server
mcp_server = MCPServerSse(
    url="https://roxyapi.com/mcp/astrology-api",
    headers={"X-API-Key": "YOUR_API_KEY"}
)

# Create agent with astrology tools
agent = Agent(
    name="astrology_assistant",
    instructions="""You are an expert astrologer and spiritual guide.
    When users ask about their birth chart, horoscope, or compatibility,
    use the available tools to calculate accurate data, then interpret
    the results in a warm, insightful way. Always ask for birth date,
    time, and location if not provided.""",
    mcp_servers=[mcp_server]
)

# Run conversation
result = await Runner.run(agent, "What does my birth chart look like?")

For Claude Desktop:

Edit your claude_desktop_config.json:

{
  "mcpServers": {
    "roxyapi-astrology": {
      "url": "https://roxyapi.com/mcp/astrology-api",
      "headers": {
        "X-API-Key": "YOUR_API_KEY"
      }
    }
  }
}

Restart Claude Desktop. Now Claude can generate birth charts, draw tarot cards, and calculate numerology just by asking.

For Gemini (Google ADK):

from google.adk.agents import LlmAgent
from google.adk.tools.mcp_tool import McpToolset
from google.adk.tools.mcp_tool.mcp_session_manager import SseConnectionParams

agent = LlmAgent(
    model="gemini-2.0-flash",
    name="astrology_assistant",
    instruction="You are an expert astrologer...",
    tools=[McpToolset(connection_params=SseConnectionParams(
        url="https://roxyapi.com/mcp/astrology-api",
        headers={"X-API-Key": "YOUR_API_KEY"}
    ))]
)

With any of these setups, the AI agent can now call any of the 85+ RoxyAPI endpoints as tools. It knows what parameters each endpoint needs, what data it returns, and how to combine results from multiple endpoints into a single response.

Saturday Afternoon: Build the Chat Interface

Step 4: Create the Frontend

The frontend is a standard chat interface. Users type messages, the AI responds. Use whatever framework you prefer.

Minimal Next.js setup:

npx create-next-app@latest astrology-app --typescript --tailwind
cd astrology-app
npm install openai  # or @anthropic-ai/sdk

Create an API route that handles the conversation:

// app/api/chat/route.ts
import OpenAI from "openai";

const client = new OpenAI();

export async function POST(req: Request) {
  const { messages } = await req.json();

  const response = await client.responses.create({
    model: "gpt-4o",
    input: messages,
    tools: [{
      type: "mcp",
      server_label: "astrology",
      server_url: "https://roxyapi.com/mcp/astrology-api",
      headers: { "X-API-Key": process.env.ROXYAPI_KEY! }
    }]
  });

  return Response.json({ message: response.output_text });
}

The frontend is a simple chat component that posts messages to this route and displays responses. Use any UI library (shadcn/ui, Basecoat, plain Tailwind).

Step 5: Add Conversation Context

The best astrology chatbots remember user details. When someone shares their birth date once, the bot should not ask again.

Store birth details in the conversation context or a lightweight database:

const systemPrompt = `You are an expert astrologer and spiritual guide.
When a user provides their birth details, remember them for the conversation.
Always use their actual birth data for calculations, not generic horoscopes.
Combine astrological insights with practical life advice.
Be warm, specific, and empathetic in your interpretations.`;

With MCP, the AI automatically calls the right endpoints. If someone asks "Am I compatible with my partner who is a Leo?", the agent will:

  1. Ask for both birth details if not already known
  2. Call the synastry endpoint with both charts
  3. Call the compatibility score endpoint
  4. Synthesize results into a natural language response about their relationship dynamics

No custom API integration code needed. The AI handles the orchestration.

Sunday: Add Polish and Ship

Step 6: Expand to Multiple Domains

Since RoxyAPI includes tarot, numerology, dreams, and I-Ching on the same plan, you can add these features with zero additional cost or integration work.

Add a second MCP server for tarot:

{
  "mcpServers": {
    "roxyapi-astrology": {
      "url": "https://roxyapi.com/mcp/astrology-api",
      "headers": { "X-API-Key": "YOUR_API_KEY" }
    },
    "roxyapi-tarot": {
      "url": "https://roxyapi.com/mcp/tarot-api",
      "headers": { "X-API-Key": "YOUR_API_KEY" }
    },
    "roxyapi-numerology": {
      "url": "https://roxyapi.com/mcp/numerology-api",
      "headers": { "X-API-Key": "YOUR_API_KEY" }
    }
  }
}

Now your app can handle:

  • "Draw me a three-card tarot spread for my career"
  • "What is my life path number? My birthday is March 15, 1992"
  • "I had a dream about falling. What does it mean?"
  • All within the same conversation, using the same API key

Step 7: Deploy

Deploy your Next.js app to Vercel, Netlify, or any hosting provider:

vercel deploy --prod

Set ROXYAPI_KEY and your AI provider key as environment variables. Your app is live.

Cost Breakdown: What This Actually Costs

Here is a realistic cost estimate for running this app in production.

Development Phase (Weekend)

Item Cost
RoxyAPI Starter plan $39/month
OpenAI API (development) ~$5
Vercel hosting (hobby) Free
Domain name ~$12/year
Total to launch ~$45

Production Phase (1,000 users)

Assuming each user averages 10 conversations/month, each conversation makes 3 API calls:

Item Monthly Cost
RoxyAPI Professional plan $149/month (50,000 requests)
OpenAI API (~30K completions) ~$60/month
Vercel Pro hosting $20/month
Total at 1,000 users ~$229/month

If you charge users $9.99/month, 1,000 users = $9,990 revenue against $229 in costs. That is a 97% gross margin.

Scaling Phase (10,000 users)

Item Monthly Cost
RoxyAPI Business plan $349/month (200,000 requests)
OpenAI API (~300K completions) ~$450/month
Vercel Pro hosting $20/month
Total at 10,000 users ~$819/month

Revenue at $9.99/month: $99,900. Costs: $819. The economics work.

What Makes This Different from Building from Scratch

Building the same capabilities without an API would require:

  • Swiss Ephemeris integration: 2-4 weeks to implement planetary calculations correctly, handle edge cases, and test against authoritative sources
  • Interpretation engine: 4-8 weeks to build a comprehensive interpretation database covering all planet-sign-house combinations
  • Tarot system: 1-2 weeks for card data, shuffle logic, spread layouts, and meaning databases
  • Numerology engine: 1-2 weeks for Pythagorean and Chaldean calculations with interpretation text
  • Infrastructure: Hosting, monitoring, timezone handling, ephemeris file management
  • Ongoing maintenance: Ephemeris updates, bug fixes, accuracy verification

Conservative estimate: 3-6 months of development time, or $50,000-$150,000 in engineering costs.

With an API, you skip all of that and go straight to building the user experience.

Common Pitfalls to Avoid

Do not hardcode birth data. Always ask users for their birth date, time, and location. Generic sun sign horoscopes are not competitive in 2026. Users expect personalized readings.

Do not skip the timezone. Astrology calculations are sensitive to timezone. A birth at 2:00 AM in New York and 2:00 AM in London produce completely different charts. Always collect the timezone offset along with the birth time.

Do not ignore the AI system prompt. The quality of your astrology chatbot depends heavily on the system prompt. Spend time crafting instructions that make the AI warm, specific, and genuinely helpful. Generic prompts produce generic responses.

Do not build your own calculation engine. Even experienced developers underestimate the complexity of astronomical calculations. Swiss Ephemeris handles precession, nutation, aberration, and relativistic effects. Your custom implementation will not.

For Developers: Technical Considerations

Response caching. Daily horoscopes are the same for all users of the same sign. Cache these responses to reduce API calls. Birth charts for the same input parameters also return identical results, so cache aggressively.

Streaming responses. AI agent responses can take 2-5 seconds for complex queries (the AI needs to call APIs and synthesize results). Use streaming to show partial responses as they generate, so users are not staring at a loading spinner.

Error handling. If the astrology API returns an error (invalid date, missing parameter), the AI agent should explain the issue to the user in natural language rather than showing raw error messages.

Rate limit awareness. Check the X-RateLimit-Remaining header on API responses. If approaching your limit, the AI should gracefully degrade (use cached data, skip optional calculations) rather than failing completely.

Ready to build your AI astrology app this weekend? RoxyAPI gives you 85+ endpoints across astrology, tarot, numerology, dreams, and I-Ching with native MCP for AI agents. Every request costs the same. View pricing or explore the API documentation.

Frequently Asked Questions

Q: Do I need to know astrology to build an astrology app? A: No. The API handles all astronomical calculations and provides interpretation data. The AI agent synthesizes this into natural language. You focus on the user experience, not the astrology logic.

Q: Which AI provider works best for astrology chatbots? A: All three major providers (OpenAI, Claude, Gemini) work well with MCP. OpenAI Agents SDK is the most straightforward for a weekend project. Claude tends to produce more empathetic, nuanced interpretations. Gemini is cost-effective for high-volume apps.

Q: How accurate are the astrology calculations? A: RoxyAPI uses Swiss Ephemeris (based on NASA JPL ephemeris data) for planetary calculations with sub-arcsecond precision. This is the same engine used by professional astrology software.

Q: Can I monetize an app built with astrology APIs? A: Yes. All paid plans allow commercial use. Common monetization models include monthly subscriptions ($5-20/user), per-reading purchases ($1-5/reading), and freemium with premium features.

Q: How many API calls does a typical user session generate? A: A birth chart reading typically requires 1-3 API calls (natal chart, possibly transits and aspects). A multi-domain session (astrology + tarot + numerology) might use 4-6 calls. Daily horoscope checks use 1 call each.

Q: What happens if my app goes viral and I exceed the request limit? A: RoxyAPI returns HTTP 429 when you hit your limit. You can upgrade plans instantly with immediate activation. The Professional plan handles 50,000 requests/month, and the Business plan handles 200,000.

Q: Can I build a mobile app instead of a web app? A: Yes. The architecture is the same. Your React Native or Flutter app talks to your backend API route, which connects to the AI agent and RoxyAPI. The MCP connection happens server-side, not on the device.

Q: Is one weekend realistic, or is that just marketing? A: If you have experience with Next.js (or similar) and have used an AI agent framework before, a working prototype in a weekend is realistic. A polished, production-ready app with user accounts, payment, and proper error handling takes 1-2 additional weeks.