MCP and JSON-RPC Transport

AMP credentials in MCP tool calls via JSON-RPC 2.0.

MCP (Model Context Protocol) is the primary transport for AI agent tool calls. AMP supports MCP as a first-class transport with per-tool pricing.

Discovery

An AMP-enabled MCP server advertises pricing via a dedicated amp/pricing method:

// Request
{ "jsonrpc": "2.0", "method": "amp/pricing", "id": 1 }
 
// Response
{
  "jsonrpc": "2.0",
  "id": 1,
  "result": {
    "amp_version": "1.0",
    "recipient": "<server_pubkey>",
    "program_id": "2d1B2PmumwYWuR82AbXAARTL1nrn8N7Vu9bLXTXUDmVA",
    "network": "solana:mainnet-beta",
    "pricing": {
      "tools": {
        "generate_image": { "mode": "per-call", "rate": "50000" },
        "search_web": { "mode": "per-call", "rate": "5000" }
      }
    }
  }
}

Each MCP tool can have its own rate and metering mode.

Channel credentials in tool calls

Include AMP credentials in the _amp field of params:

{
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "name": "generate_image",
    "arguments": { "prompt": "a cat in space" },
    "_amp": {
      "channel": "<channel_pda_base58>",
      "seq": 42,
      "sig": "<ed25519_sig_base58>"
    }
  },
  "id": 2
}

The _amp field is a reserved namespace. MCP servers that don't support AMP ignore fields prefixed with _.

Payment required response

If a tool call lacks credentials:

{
  "jsonrpc": "2.0",
  "id": 2,
  "error": {
    "code": -32602,
    "message": "AMP_NO_CHANNEL",
    "data": {
      "amp_pricing": {
        "mode": "per-call",
        "rate": "50000",
        "recipient": "<server_pubkey>"
      }
    }
  }
}

Server SDK

import { AMPMcpServer } from "@valeo/amp-server"
 
const server = new AMPMcpServer({
  wallet: serverKeypair,
  connection,
  tools: {
    generate_image: {
      description: "Generate an image",
      pricing: { mode: "per-call", rate: "50000", token: "...", minDeposit: "1000000", settleInterval: 3600 },
      inputSchema: { type: "object", properties: { prompt: { type: "string" } } },
      handler: async (args, amp) => ({ url: "..." }),
    },
  },
})

Client SDK

import { AMPMcpClient } from "@valeo/amp-client"
 
const client = new AMPMcpClient({ wallet, connection, budget: 5.0 })
await client.connect("http://localhost:3000/mcp")
 
const result = await client.callTool("generate_image", { prompt: "cat" })
await client.close()