API Documentation

Overview

AgentNDX exposes free static JSON endpoints plus Railway-backed API routes for live index access. Some endpoints are free. Compute-heavy endpoints can use the x402 protocol — pay per query in USDC on Base mainnet. API Pro uses a regular X-Api-Key header for teams that do not want crypto in the request path.

Free Endpoints

GET /api/servers.json Full curated server index (JSON)

GET /api/stats.json Total indexed, MCP count, A2A count, x402 count

GET /api/categories.json Category list with server counts

x402 Endpoints

These endpoints return 402 Payment Required on first call. Pay via x402 protocol and retry with X-PAYMENT header.

GET /api/search?q=&limit=&category= Full search across the live Railway index — semantic + keyword $0.005 USDC

MCP Endpoint

AgentNDX exposes a public MCP-style JSON-RPC endpoint at https://agentndx.ai/mcp. Search is x402-paid; details, categories, and stats are free.

# MCP server config
{
  "mcpServers": {
    "agentndx": {
      "command": "npx",
      "args": ["-y", "mcp-remote", "https://agentndx.ai/mcp"]
    }
  }
}

TOOL search_mcp_servers(query, category?, limit?) $0.005 USDC

TOOL get_server_details(id) Free

TOOL list_categories() Free

TOOL get_stats() Free

Payment Flow

x402 is a standard HTTP payment flow. No account or API key is needed for x402-paid requests. API Pro uses an API key instead.

# Step 1: make request, get 402 back
GET /api/search?q=filesystem

HTTP/1.1 402 Payment Required
X-PAYMENT-REQUIRED: {"amount":"0.005","currency":"USDC","network":"base","recipient":"0x..."}

# Step 2: sign USDC payment on Base mainnet
# Step 3: retry with X-PAYMENT header
GET /api/search?q=filesystem
X-PAYMENT: <signed-payment-proof>

HTTP/1.1 200 OK
{ "results": [...] }

Use x402 client libraries for automated payment flows in your agent.

Rate Limits

Free endpoints: 60 requests/minute per IP.
Paid endpoints: no artificial limits — each payment is a separate transaction.
Abusive patterns (replay attacks, scraping at scale) will be blocked.