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rplryan
rplryan

Posted on • Originally published at x402-discovery-api.onrender.com

x402 Service Discovery: How Autonomous Agents Find and Pay for APIs at Runtime

#x402 #agents #python #micropayments

x402 Service Discovery: How Autonomous Agents Find and Pay for APIs at Runtime

Autonomous agents need to call paid APIs. The problem: there's no standard way to find them.

You don't want to hardcode 50 endpoint URLs into your agent. You want it to discover the best available service for any capability at runtime — like DNS for the agent economy.

That's what x402 Service Discovery does.

What is x402?

x402 is a protocol that lets HTTP servers charge for API calls using USDC stablecoin micropayments on Base. A client hits an endpoint, gets a 402 Payment Required response with a payment challenge, pays ~$0.001–$0.05 in USDC, then retries the request with a payment proof header. No API keys, no subscriptions, no billing dashboards.

The discovery problem

The x402 ecosystem is growing — there are services for research, data feeds, compute, AI agents — but there's no index. You have to know a URL exists before you can call it.

We built the missing piece: a service registry where x402-payable APIs can register themselves, and agents can query by capability.

How it works

Free: Browse the full catalog 

curl https://x402-discovery-api.onrender.com/catalog
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Gated: Query by capability (x402 payment required) 

curl "https://x402-discovery-api.onrender.com/discover?q=research+API"
# → 402 Payment Required
# x-payment-required: {"payTo": "0xDBBe14C418466Bf5BF0ED7638B4E6849B852aFfA", "amount": "5000", ...}
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Cost: $0.005 USDC per query. Payment handled automatically by x402-capable clients.

Python SDK 

pip install x402discovery
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Framework integrations

Now supporting 6 frameworks:

1. Coinbase AgentKit (NEW ✨)

The natural home for x402 — AgentKit agents already have a funded Base/USDC wallet. The x402_pay_and_call action closes the full loop: discover → pay → execute, all in one step.

pip install agentkit-x402-discovery
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from agentkit_x402_discovery import x402_discovery_action_provider
from coinbase_agentkit import AgentKit, AgentKitConfig

agent_kit = AgentKit(AgentKitConfig(
    wallet_provider=wallet_provider,
    action_providers=[
        x402_discovery_action_provider(),
        # ... your other providers
    ]
))

# Your agent now has 4 new actions:
# x402_discover  — Find services by keyword/capability
# x402_browse    — List full catalog (free, no payment)
# x402_health    — Check service uptime & latency
# x402_pay_and_call — Discover + pay + call in one shot
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2. LangChain 

pip install langchain-x402-discovery
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from langchain_x402_discovery import X402DiscoveryTool
from langchain.agents import initialize_agent, AgentType
from langchain_openai import ChatOpenAI

llm = ChatOpenAI(model="gpt-4o")
tools = [X402DiscoveryTool()]
agent = initialize_agent(tools, llm, agent=AgentType.OPENAI_FUNCTIONS)
agent.run("Find a research API under $0.05/call")
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3. AutoGen 

pip install autogen-x402-discovery
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4. CrewAI 

pip install crewai-x402-discovery
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5. LlamaIndex 

pip install llama-index-x402-discovery
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6. Raw Python 

from x402discovery import X402DiscoveryClient
client = X402DiscoveryClient()
results = client.discover(query="weather data", max_price_usd=0.10)
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MCP (Model Context Protocol)

Available as an MCP server on Smithery with 5 tools: x402_discover, x402_browse, x402_health, x402_register, x402_trust.

Trust Layer: ERC-8004 Integration (NEW ✨)

Beyond quality signals (uptime, latency), we now surface on-chain trust identity for every registered service.

ERC-8004 is a new Ethereum standard (January 2026) that provides decentralized AI agent trust via three on-chain registries:

  • Identity Registry — unique on-chain identifier for each agent/service
  • Reputation Registry — verifiable scores from real interactions
  • Validation Registry — third-party attestations from auditors and ecosystem partners

Every service in our catalog now returns trust fields alongside quality signals:

{
  "name": "My x402 API",
  "uptime_pct": 99.1,
  "avg_latency_ms": 145,
  "erc8004_verified": true,
  "erc8004_reputation_score": 87,
  "erc8004_attestations": 3,
  "erc8004_source": "well-known"
}
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New: /trust/{wallet} endpoint

Look up the ERC-8004 trust profile for any wallet address:

curl https://x402-discovery-api.onrender.com/trust/0xDBBe14C418466Bf5BF0ED7638B4E6849B852aFfA
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Returns identity metadata, reputation score, and attestation count — sourced from the ERC-8004 on-chain registries and /.well-known/erc8004.json declarations.

New MCP tool: x402_trust

The MCP server now exposes 5 tools (up from 4):

Tool What it does Cost
x402_discover Search services by keyword/capability $0.005 USDC
x402_browse Browse full catalog by category Free
x402_health Check uptime & latency Free
x402_register Register your service Free
x402_trust Look up ERC-8004 trust profile for any wallet Free

The demo at rplryan.github.io/ouroboros/demo.html shows ERC-8004 verification badges on services that have declared on-chain identity.

Register your x402 service 

import requests
requests.post("https://x402-discovery-api.onrender.com/register", json={
    "id": "my-service",
    "name": "My x402 API",
    "url": "https://my-api.com/endpoint",
    "price_usd": 0.01,
    "description": "Does something useful",
    "capability_tags": ["data", "research"],
    "wallet_address": "0xYOUR_WALLET",
    "network": "base"
})
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Registration is free. Health monitoring is automatic. Once registered, your service gets ERC-8004 trust lookup automatically if your wallet has an on-chain identity.

What's next

The catalog grows as more x402 services register. Quality signals (uptime_pct, avg_latency_ms, health_status) plus ERC-8004 trust scores let agents prefer reliable, verified services — the full trust layer the x402 ecosystem needs.

Links:

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