Built 17 x402-gated APIs + a dynamic MCP package as a solo indie dev — here's everything

#ai #mcp #web3 #buildinpublic

What I built

Over the past few weeks I shipped 17 production APIs — all x402/USDC micropayment gated,
all MCP compatible, all deployed on Railway under my own domain yantrix.ai.

Here's the full list:

API	What it does	Price
groundtruth.yantrix.ai	Fact verification for agents	$0.002–$0.020
memex.yantrix.ai	Persistent agent memory	$0.001–$0.005
indic.yantrix.ai	Indian language NLP (9 scripts)	$0.001–$0.008
contractscan.yantrix.ai	Contract risk analysis	$0.005–$0.025
threatmodel.yantrix.ai	STRIDE threat modelling	$0.005–$0.025
signal.yantrix.ai	AI trend intelligence	$0.005–$0.020
compwatch.yantrix.ai	Competitor intelligence	$0.010–$0.020
examforge.yantrix.ai	Exam generator	$0.005–$0.020
voiceprint.yantrix.ai	Writing style transfer	$0.003–$0.010
papertrail.yantrix.ai	Indian regulatory intel	$0.003–$0.015
ratelord.yantrix.ai	Rate limit coordinator	$0.0005–$0.001
heatmap.yantrix.ai	API usage analytics	$0.0001–$0.015
debateclub.yantrix.ai	Argument generator	$0.003–$0.010
callsight.yantrix.ai	Sales call intelligence	$0.010–$0.025
phonevalidator.yantrix.ai	Global phone validation	$0.001
ifsclookup.yantrix.ai	Indian bank IFSC lookup	$0.001
timezonedetective.yantrix.ai	Timezone detection	$0.001–$0.002

What is x402?

x402 is an open payment protocol by Coinbase built on HTTP 402 "Payment Required".
Instead of API keys and billing dashboards, agents pay per call using USDC on Base.
No accounts. No monthly invoices. Just pay and get the resource.

Agent calls API → gets 402 with payment terms → pays USDC → gets response

The MCP package

Instead of building a static MCP server, I built a dynamic one.

The package fetches its tool list from a live registry at startup:

npx @praveen030686/yantrix-mcp

When I add a new API, I update one JSON file on the server. All users get the
new tool automatically on next restart. No npm republish ever needed.

Adding a new API takes 10 lines

# In mcp-registry/main.py, add to TOOLS list:
{
    "name": "new_tool",
    "service": "newapi",
    "endpoint": "https://newapi.yantrix.ai/endpoint",
    "method": "POST",
    "description": "What it does.",
    "input_schema": {...},
    "cost_usdc": "0.005",
    "category": "category",
}
# git push → Railway redeploys → users get new tool automatically

Tech stack

Backend: FastAPI (Python 3.11)
Payments: x402 + USDC on Base Mainnet
AI: Claude API (Sonnet + Haiku)
Deployment: Railway (one service per API)
MCP: TypeScript MCP SDK
Domain: Spaceship + custom subdomains per API

Claude Desktop config

{
  "mcpServers": {
    "yantrix": {
      "command": "npx",
      "args": ["@praveen030686/yantrix-mcp"],
      "env": {
        "DEV_MODE": "true"
      }
    }
  }
}