openrpc-mpc-server
by shanejonas
#!/usr/bin/env node
import { RequestManager, HTTPTransport, Client } from "@open-rpc/client-js";
/**
* This is an OpenRPC server that provides JSON-RPC functionality.
* It allows:
* - Discovering JSON-RPC methods via rpc.discover
* - Calling arbitrary JSON-RPC methods
*/
import { Server } from "@modelcontextprotocol/sdk/server/index.js";
import { StdioServerTransport } from "@modelcontextprotocol/sdk/server/stdio.js";
import {
CallToolRequestSchema,
ListToolsRequestSchema,
} from "@modelcontextprotocol/sdk/types.js";
/**
* Create an MCP server with capabilities for tools and prompts
* to interact with JSON-RPC servers
*/
const server = new Server(
{
name: "openrpc",
version: "0.1.0",
},
{
capabilities: {
resources: {},
tools: {},
prompts: {},
},
}
);
/**
* Handler that lists available tools.
* Exposes two tools:
* - rpc_call: For calling arbitrary JSON-RPC methods
* - rpc_discover: For discovering available methods on a server
*/
server.setRequestHandler(ListToolsRequestSchema, async () => {
return {
tools: [
{
name: "rpc_call",
description: "Call any JSON-RPC method on a server with parameters. A user would prompt: Call method <method> on <server url> with params <params>",
inputSchema: {
type: "object",
properties: {
server: {
type: "string",
description: "Server URL"
},
method: {
type: "string",
description: "JSON-RPC method name to call"
},
// this is a bit of a hack since claude seems to have issues with nested parameters
params: {
type: "string",
description: "Stringified Parameters to pass to the method"
}
},
required: ["server", "method"]
}
},
{
name: "rpc_discover",
description: "This uses JSON-RPC to call `rpc.discover` which is part of the OpenRPC Specification for discovery for JSON-RPC servers. A user would prompt: What JSON-RPC methods does this server have? <server url>",
inputSchema: {
type: "object",
properties: {
server: {
type: "string",
description: "Server URL"
},
},
required: ["server"]
}
}
]
};
});
/**
* Handler for JSON-RPC tools.
* Handles both method discovery and arbitrary method calls.
*/
server.setRequestHandler(CallToolRequestSchema, async (request) => {
switch (request.params.name) {
case "rpc_call": {
const server = String(request.params.arguments?.server);
const method = String(request.params.arguments?.method);
const params = JSON.parse(String(request.params.arguments?.params));
let transport = new HTTPTransport(server);
let client = new Client(new RequestManager([transport]));
const results = await client.request({ method: method, params: params as any});
return {
toolResult: {
content: [{
type: "text",
text: JSON.stringify(results, null, 2)
}],
isError: false
}
};
}
case "rpc_discover": {
const server = String(request.params.arguments?.server);
if (!server) {
throw new Error("Server is required");
}
let transport = new HTTPTransport(server);
let client = new Client(new RequestManager([transport]));
const results = await client.request({ method: "rpc.discover" });
return {
toolResult: {
content: [{
type: "text",
text: JSON.stringify(results, null, 2)
}],
isError: false
}
};
}
default:
throw new Error("Unknown tool");
}
});
/**
* Start the server using stdio transport.
* This allows the server to communicate via standard input/output streams.
*/
async function main() {
const transport = new StdioServerTransport();
await server.connect(transport);
}
main().catch((error) => {
console.error("Server error:", error);
process.exit(1);
});