Agents & payments

MCP server

Arca ships an MCP server so any MCP client - Claude Desktop, Cursor, agent frameworks - can call Arca models as tools: list_models, chat, embed, and estimate_cost.

Auth modes

Two auth modes, auto-detected from env. Keyed: set ARCA_API_KEY to use your prepaid balance. x402: set EVM_PRIVATE_KEY (0x hex) instead and the agent pays per call in USDG on Robinhood Chain from that wallet - no account at all (chat only). Use a dedicated, low-balance wallet for this.

mcp config (keyed)

{
  "mcpServers": {
    "arca": {
      "command": "npx",
      "args": ["-y", "@arca/mcp"],
      "env": { "ARCA_API_KEY": "ar_sk_live_…" }
    }
  }
}

mcp config (x402 pay-per-call)

{
  "mcpServers": {
    "arca": {
      "command": "npx",
      "args": ["-y", "@arca/mcp"],
      "env": {
        "EVM_PRIVATE_KEY": "0x… private key (burner wallet)"
      }
    }
  }
}

Install

The package is on npm as @arca/mcp - npx fetches it automatically, so the configs above work as-is. Restart your MCP client after adding one.