Stoa

A decentralized AI services marketplace with on-chain USDC payments

Discover, call, and pay for AI/ML services — directly from Claude Desktop, Cursor, or any MCP client. Providers register endpoints. Consumers pay per-call in USDC. Payments settle on-chain via the x402 protocol.

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 Table of Contents 

 

• What is Stoa
• Architecture
• Monorepo Structure
• Tech Stack
• Live Deployments
• How It Works
  • Service Discovery
  • Payment Flow (x402)
  • Authentication
  • MCP Integration
• Database Schema
• API Reference
• Getting Started
• Environment Variables
• Deployment
• Team

 

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What is Stoa

Stoa is a full-stack AI services marketplace where:

• Providers register ML models, AI agents, or API tools — set a price in USDC, and earn per call
• Consumers discover services via semantic search, call them, and pay automatically on-chain
• AI assistants (Claude, Cursor) interact with the marketplace natively through MCP tools — search, call, and pay without leaving the conversation

The entire payment layer runs on Base Sepolia using the x402 HTTP payment protocol — no smart contract deployment needed. Services are discoverable via pgvector semantic search powered by HuggingFace embeddings.

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Architecture

                         C O N S U M E R S
    ┌──────────────┐    ┌──────────────┐    ┌──────────────┐
    │   Web App    │    │    Claude    │    │   Agent SDK  │
    │  (Next.js)   │    │   Desktop   │    │  (TypeScript)│
    └──────┬───────┘    └──────┬───────┘    └──────┬───────┘
           │                   │                    │
           │            ┌──────┴───────┐            │
           │            │  MCP Server  │            │
           │            │  (16+ tools) │            │
           │            └──────┬───────┘            │
           │                   │                    │
           ▼                   ▼                    ▼
    ╔══════════════════════════════════════════════════════╗
    ║              S T O A   A P I   (Hono)               ║
    ║                                                      ║
    ║  ┌────────┐  ┌──────────┐  ┌────────┐  ┌────────┐  ║
    ║  │  Auth  │  │ Services │  │ Wallet │  │  x402  │  ║
    ║  │ Routes │  │  Routes  │  │ Routes │  │  Proxy │  ║
    ║  └────┬───┘  └────┬─────┘  └────┬───┘  └────┬───┘  ║
    ║       └────────────┴─────────────┴───────────┘      ║
    ║            Drizzle ORM  +  pgvector                  ║
    ╚═══════════════════════╤══════════════════════════════╝
                            │
              ┌─────────────┼─────────────┐
              ▼             ▼             ▼
        ┌──────────┐  ┌──────────┐  ┌──────────┐
        │ Supabase │  │ Coinbase │  │    HF    │
        │ Postgres │  │   CDP    │  │  Spaces  │
        └──────────┘  └──────────┘  └──────────┘

---

Monorepo Structure

stoa/
│
├── apps/
│   ├── web/                   Next.js 16 frontend
│   │                          thirdweb wallet, Radix UI, Framer Motion
│   │
│   └── mcp-server/            MCP server for Claude Desktop & Cursor
│                              16+ tools: search, call, pay, manage
│
├── packages/
│   ├── server/                Hono API backend
│   │                          auth, services, wallet, x402, razorpay
│   │
│   ├── db/                    Drizzle ORM + pgvector
│   │                          schema, queries, semantic search
│   │
│   ├── shared/                Zod schemas, TypeScript types, constants
│   │
│   ├── agent-sdk/             TypeScript SDK for the Stoa API
│   │
│   └── contracts/             Smart contract stubs
│
├── services/
│   ├── chest-xray-service/    Pneumonia detection (ViT, HF Spaces)
│   ├── plant-disease-service/ Plant disease ID (MobileNetV2, HF Spaces)
│   └── digital-twin-agent/    AI personality service (FastAPI)
│
├── scripts/
│   └── seed-services.ts       Seed marketplace with starter data
│
├── Dockerfile                 Multi-stage build for Railway
├── turbo.json                 Turborepo pipeline
└── pnpm-workspace.yaml        Workspace definition

Package dependency graph:

shared ──────┐
             ├──► server ──► Docker ──► Railway
db ──────────┘
                    │
mcp-server ◄────────┤  (calls API over HTTP)
web ◄───────────────┤  (calls API over HTTP)
agent-sdk ◄─────────┘  (calls API over HTTP)

---

Tech Stack

Layer	Technology
Frontend	Next.js 16 · React 19 · TailwindCSS 4 · Radix UI · Framer Motion · Recharts
Backend	Hono 4 · Node.js 24 · TypeScript 5.7
Database	PostgreSQL (Supabase) · Drizzle ORM · pgvector
Blockchain	Base Sepolia · USDC · Viem 2 · Coinbase CDP SDK
Payments	x402 Protocol v2 · @x402/hono · @x402/fetch · @x402/evm
Wallet	thirdweb 5 (frontend) · Coinbase CDP (backend managed)
Embeddings	HuggingFace Inference · nomic-embed-text-v1.5 (768-dim)
AI Models	HuggingFace Spaces · FastAPI + Docker
MCP	@modelcontextprotocol/sdk · stdio + SSE transport
Auth	JWT · bcrypt · API keys · Google OAuth (Supabase)
Fiat Onramp	Razorpay (INR to USDC)
Monorepo	pnpm 9 · Turborepo 2
Deployment	Railway (API) · Vercel (Web) · HuggingFace Spaces (ML)

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Live Deployments

Service	URL	Status
API Backend	https://stoa-api-production-58bd.up.railway.app	Railway
Health Check	https://stoa-api-production-58bd.up.railway.app/health	GET
Chest X-ray Model	https://hiteshx33-chest-xray-service.hf.space	HF Spaces
Plant Disease Model	https://hiteshx33-plant-disease-service.hf.space	HF Spaces
Database	Supabase PostgreSQL + pgvector	Supabase
Blockchain	Base Sepolia · Chain ID 84532	Testnet
USDC Contract	0x036CbD53842c5426634e7929541eC2318f3dCF7e	Base Sepolia

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How It Works

Service Discovery

Services are registered with metadata, capabilities, and pricing. Each service gets a 768-dimensional embedding (via nomic-embed-text-v1.5) stored in a pgvector column. Discovery uses cosine similarity search:

User query: "detect pneumonia from medical images"
                    │
                    ▼
         ┌─────────────────────┐
         │  Generate embedding  │  HuggingFace Inference API
         │  (768 dimensions)    │
         └──────────┬──────────┘
                    │
                    ▼
         ┌─────────────────────┐
         │  pgvector cosine    │  PostgreSQL + Drizzle
         │  similarity search   │
         └──────────┬──────────┘
                    │
                    ▼
         ┌─────────────────────┐
         │  Ranked results     │  Sorted by match score
         │  with confidence    │
         └─────────────────────┘

Payment Flow (x402)

Consumer                     Stoa API                     Provider
   │                            │                            │
   │  POST /v1/call/:id         │                            │
   │  ──────────────────────►   │                            │
   │                            │                            │
   │  402 + PAYMENT-REQUIRED    │                            │
   │  ◄──────────────────────   │                            │
   │                            │                            │
   │  Same request +            │                            │
   │  PAYMENT-SIGNATURE header  │                            │
   │  ──────────────────────►   │                            │
   │                            │  Forward to endpoint       │
   │                            │  ──────────────────────►   │
   │                            │                            │
   │                            │  Result                    │
   │                            │  ◄──────────────────────   │
   │                            │                            │
   │  Result + txHash +         │  Settle on-chain (async)   │
   │  basescanUrl               │                            │
   │  ◄──────────────────────   │                            │

Three payment modes:

Mode	When	How
x402 (on-chain)	MCP/SDK with wallet key	USDC signed via Viem, settled on Base Sepolia
API Key auth	X-Stoa-Key header	Cost tracked in DB, deducted from balance
Free / Test	priceUsdcPerCall = 0 or ?test=true	Direct call, no payment

Authentication

┌─────────────┐      ┌─────────────┐      ┌─────────────┐
│  Email /    │      │   Google    │      │   Wallet    │
│  Password   │      │   OAuth     │      │  (thirdweb) │
└──────┬──────┘      └──────┬──────┘      └──────┬──────┘
       │                    │                     │
       ▼                    ▼                     ▼
╔═════════════════════════════════════════════════════════╗
║                    Stoa Auth Layer                       ║
║                                                         ║
║  JWT Token  ◄───  User Record  ───►  API Key            ║
║  (session)       (PostgreSQL)        (X-Stoa-Key)       ║
╚═════════════════════════════════════════════════════════╝

• JWT Bearer tokens — web sessions (POST /api/auth/login)
• API keys — SDK, MCP, and programmatic access (X-Stoa-Key header)
• Wallet linking — connect your own wallet or auto-provision a CDP managed wallet

MCP Integration

The MCP server exposes 16+ tools that Claude Desktop or Cursor can call natively:

Category	Tools
Account	create_account · login
Discovery	find_service · list_services · get_service_schema · get_activity · get_provider
ML Inference	analyze_xray · analyze_plant
Service Calls	call_service (with automatic x402 payment)
Wallet	get_wallet_status · fund_wallet · withdraw · get_usage
Provider	register_service · my_services · update_service · deactivate_service

Claude Desktop config:

{
  "mcpServers": {
    "stoa": {
      "command": "npx",
      "args": ["@stoa/mcp-server"],
      "env": {
        "STOA_API_KEY": "stoa_your_key_here",
        "WALLET_PRIVATE_KEY": "0x..."
      }
    }
  }
}

---

Database Schema

┌──────────────────────┐         ┌──────────────────────────┐
│       users           │         │        services           │
├──────────────────────┤         ├──────────────────────────┤
│ id          uuid PK   │◄────────│ userId        uuid FK    │
│ email       unique     │         │ id            uuid PK    │
│ passwordHash           │         │ ownerAddress             │
│ walletAddress          │         │ name                     │
│ cdpWalletId            │         │ description              │
│ displayName            │         │ capabilities    jsonb    │
│ googleId               │         │ category                 │
│ createdAt              │         │ serviceType              │
└──────────┬────────────┘         │ priceUsdcPerCall numeric │
           │                      │ endpointUrl              │
           │                      │ embedding     vector(768)│
           │                      │ totalCalls               │
           │                      │ successRate              │
           │                      │ isActive                 │
           │                      │ isVerified               │
           │                      └──────────┬───────────────┘
           │                                 │
  ┌────────┴─────────────┐         ┌─────────┴──────────────┐
  │      api_keys         │         │       call_logs         │
  ├──────────────────────┤         ├────────────────────────┤
  │ id          uuid PK   │         │ id          uuid PK    │
  │ userId      uuid FK   │         │ serviceId   uuid FK    │
  │ keyHash     sha256    │         │ userId      uuid FK    │
  │ keyPrefix             │         │ callerAddress          │
  │ label                 │         │ costUsdc               │
  │ revokedAt             │         │ txHash                 │
  └──────────────────────┘         │ latencyMs              │
                                   │ success                │
  ┌──────────────────────┐         └────────────────────────┘
  │  topup_transactions   │
  ├──────────────────────┤
  │ id          uuid PK   │
  │ userId      uuid FK   │
  │ amountInr             │
  │ amountUsdc            │
  │ razorpayOrderId       │
  │ status                │
  └──────────────────────┘

Key indexes: category, ownerAddress, isActive, serviceType, embedding (pgvector)

---

API Reference

 Authentication 

 

Method	Endpoint	Description
POST	/api/auth/register	Create account (email + password) — returns API key
POST	/api/auth/login	Login — returns JWT token
POST	/api/auth/google	Google OAuth via Supabase access token
GET	/api/auth/me	Current user profile (JWT or API key)

 

 Services 

 

Method	Endpoint	Description
POST	/api/services	Register a new service
POST	/api/services/search	Semantic search (pgvector embeddings)
GET	/api/services	List services (filters: category, type, sort, limit, offset)
GET	/api/services/:id	Service details + recent call logs
PUT	/api/services/:id	Update service (owner auth required)
DELETE	/api/services/:id	Deactivate service (owner auth required)
POST	/api/services/:id/verify	Verify endpoint is reachable
POST	/api/services/:id/embedding	Regenerate embedding vector

 

 Service Calls (x402) 

 

Method	Endpoint	Description
POST	/v1/call/:serviceId	Call a service — x402 payment or API key auth

Returns: { result, cost, txHash, basescanUrl, latencyMs }

 

 Wallet 

 

Method	Endpoint	Description
POST	/api/wallet/link	Link external wallet address
GET	/api/wallet/balance	Current USDC balance (on-chain)
GET	/api/wallet/address	Get or auto-create wallet address
GET	/api/wallet/transactions	Call history with costs
GET	/api/wallet/usage	Aggregate usage stats
POST	/api/wallet/topup/razorpay	Create Razorpay order (INR to USDC)
POST	/api/wallet/topup/razorpay/verify	Verify Razorpay payment
GET	/api/wallet/topup/history	Top-up transaction history

 

 Providers & Activity 

 

Method	Endpoint	Description
GET	/api/providers/:userId	Provider profile + stats
GET	/api/providers/:userId/services	Provider's registered services
GET	/api/activity	Recent marketplace activity feed

 

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Getting Started

Prerequisites

Requirement	Version
Node.js	>= 20
pnpm	>= 9
PostgreSQL	with pgvector extension

# Enable pnpm via corepack
corepack enable && corepack prepare pnpm@latest --activate

Install & Run

# 1 — Clone the repo
git clone <repo-url> && cd stoa

# 2 — Install all dependencies
pnpm install

# 3 — Configure environment
cp .env.example .env
# Fill in all required values (see next section)

# 4 — Push database schema
pnpm --filter @stoa/db drizzle-kit push

# 5 — Seed the marketplace
pnpm seed

# 6 — Start everything
pnpm dev

Service	Default URL
API	http://localhost:3001
Web	http://localhost:3000

Run Individual Packages

# API server only
pnpm --filter @stoa/server dev

# Web frontend only
pnpm --filter @stoa/web dev

# MCP server (stdio mode)
cd apps/mcp-server && node dist/index.js

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Environment Variables

packages/server — API Backend

Variable	Required	Description
DATABASE_URL	Yes	PostgreSQL connection (transaction pooler, port 6543)
DATABASE_URL_DIRECT	Migrations	Direct connection (port 5432)
JWT_SECRET	Yes	Secret for signing JWT tokens
HF_TOKEN	Yes	HuggingFace API token
HF_EMBEDDING_MODEL	—	Default: nomic-ai/nomic-embed-text-v1.5
EMBEDDING_DIMENSIONS	—	Default: 768
CDP_API_KEY_ID	Yes	Coinbase CDP API key ID
CDP_API_KEY_SECRET	Yes	Coinbase CDP API key secret
CDP_WALLET_SECRET	—	CDP wallet encryption secret
X402_FACILITATOR_URL	—	Default: Coinbase facilitator
RAZORPAY_KEY_ID	Yes	Razorpay key
RAZORPAY_KEY_SECRET	Yes	Razorpay secret
SUPABASE_SERVICE_ROLE_KEY	Google OAuth	Supabase service role key
PORT	—	Default: 3001

apps/web — Frontend

Variable	Required	Description
NEXT_PUBLIC_API_URL	Yes	Stoa API URL
NEXT_PUBLIC_THIRDWEB_CLIENT_ID	Yes	thirdweb project client ID
NEXT_PUBLIC_RAZORPAY_KEY_ID	Yes	Razorpay public key
NEXT_PUBLIC_SUPABASE_URL	Yes	Supabase project URL
NEXT_PUBLIC_SUPABASE_ANON_KEY	Yes	Supabase anon key

apps/mcp-server — MCP Tools

Variable	Required	Description
STOA_API_URL	—	Default: production Railway URL
STOA_API_KEY	Yes	User's API key for authenticated calls
WALLET_PRIVATE_KEY	For x402	Private key for on-chain payment signing

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Deployment

API Backend → Railway

The multi-stage Dockerfile builds shared → db → server:

FROM node:24-slim AS base
RUN corepack enable && corepack prepare pnpm@latest --activate
WORKDIR /app
COPY package.json pnpm-workspace.yaml pnpm-lock.yaml turbo.json tsconfig.base.json ./
COPY packages/shared/ packages/shared/
COPY packages/db/ packages/db/
COPY packages/server/ packages/server/
RUN pnpm install --frozen-lockfile && pnpm run build
EXPOSE 3001
CMD ["node", "packages/server/dist/index.js"]

Set all server env vars in Railway dashboard. Port: 3001.

Frontend → Vercel

cd apps/web && vercel deploy

Set NEXT_PUBLIC_* variables in Vercel project settings.

ML Models → HuggingFace Spaces

Each service in services/ is a standalone FastAPI app deployed as a Docker Space:

Service	Space
Chest X-ray detection	hiteshx33-chest-xray-service
Plant disease detection	hiteshx33-plant-disease-service
Digital twin agent	HF Spaces (Docker SDK)

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Team

Built by Team Stoa for the Inceptrix Hackathon.

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_{Base Sepolia · x402 Protocol · Coinbase CDP · HuggingFace · thirdweb}