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March 29, 2025 17:05
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converting oRPC routers to MCP tools - beginning, it's buggy.. can't figure out how to provide the procedure's inputSchema as mcp tool schema... should be `inputSchema.shape` but.. it errors
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| interface McpToolResult { | |
| content: Array<{ type: string; text: string }>; | |
| isError?: boolean; | |
| } | |
| interface OrpcProcedureMeta { | |
| meta?: { | |
| tool_name?: string; | |
| }; | |
| route: { | |
| summary?: string; | |
| tags?: string[]; | |
| }; | |
| inputSchema: ZodSchema; | |
| handler: (input: any) => Promise<any>; | |
| } | |
| // Helper to convert procedure result to MCP format | |
| function toMcpResult(result: any): McpToolResult { | |
| return { | |
| content: [{ type: 'text', text: JSON.stringify(result) }], | |
| }; | |
| } | |
| // Helper to convert error to MCP format | |
| function toMcpError(error: any): McpToolResult { | |
| return { | |
| content: [{ type: 'text', text: error instanceof Error ? error.message : String(error) }], | |
| isError: true, | |
| }; | |
| } | |
| export function convertRouterToMcpTools(orpcRouter: any, options?: any) { | |
| const tools = new Map(); | |
| const opts = { | |
| context: {}, | |
| name: 'orpc router', | |
| version: '0.0.1', | |
| ...options, | |
| }; | |
| // Recursively walk through router to find procedures | |
| function walkRouter(node: any, path: string[] = []) { | |
| for (const [key, value] of Object.entries<any>(node)) { | |
| if (value?.['~orpc']) { | |
| // Found a procedure | |
| const procedure = value['~orpc'] as OrpcProcedureMeta; | |
| const toolName = procedure.meta?.tool_name || [...path, key].join('_'); | |
| tools.set(toolName, { | |
| name: toolName, | |
| path: (procedure.route as any)?.path?.slice(1), | |
| description: procedure.route.summary || '', | |
| inputSchema: procedure.inputSchema, | |
| handler: async (input: any) => { | |
| try { | |
| const result = await procedure.handler({ | |
| context: opts.context, | |
| input, | |
| path: toolName.split('_'), | |
| procedure: value['~orpc'], | |
| }); | |
| return toMcpResult(result); | |
| } catch (err) { | |
| return toMcpError(err); | |
| } | |
| }, | |
| }); | |
| } else if (typeof value === 'object') { | |
| // Continue walking | |
| walkRouter(value, [...path, key]); | |
| } | |
| } | |
| } | |
| walkRouter(orpcRouter); | |
| return { ...opts, tools }; | |
| } | |
| // USAGE --- | |
| const mcp = convertRouterToMcpTools(router, { | |
| name: 'orpc-contract-first-playground-demo-mcp-server', | |
| version: '0.1.0', | |
| context: { | |
| db: createFakeDB(), | |
| }, | |
| }); | |
| // Create server instance | |
| const server = new McpServer({ | |
| name: mcp.name, | |
| version: mcp.version, | |
| }); | |
| for (const [_, tool] of mcp.tools.entries()) { | |
| server.tool(tool.name, tool.inputSchema.shape, tool.handler); | |
| } | |
| async function main() { | |
| const transport = new StdioServerTransport(); | |
| await server.connect(transport); | |
| console.error('orpc contract first playground mcp server running on stdio'); | |
| } | |
| main().catch((err) => { | |
| console.error('Fatal error in main():', err); | |
| process.exit(1); | |
| }); | |
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As a reference, you may try this one by Cody: unnoq/orpc#300 (reply in thread)
It's made better and supports converting Zod v4 oRPC input schemas to Zod v3 that is required by the MCP SDK.