Ask for Input

Before your tool deletes a file, your tool must get a confirmation from the user. Call requestInput on ctx.context for that confirmation.

ctx is the second argument of the function you pass to .server(). Give .server() the type MCPToolContext, so ctx.context.requestInput type-checks.

import { toolDefinition } from '@tanstack/ai'
import { createMCPServer } from '@tanstack/ai-mcp/server'
import type { MCPToolContext } from '@tanstack/ai-mcp/server'
import { z } from 'zod'

const deleteFile = toolDefinition({
  name: 'delete_file',
  description: 'Delete a file after the user says yes',
  inputSchema: z.object({
    path: z.string(),
  }),
}).server<MCPToolContext>(async ({ path }, ctx) => {
  const answer = await ctx.context.requestInput({
    message: `Delete ${path}? Type yes to continue.`,
  })

  if (answer !== 'yes') {
    return `Kept ${path}.`
  }

  return `Deleted ${path}.`
})

const server = createMCPServer({
  name: 'files',
  version: '1.0.0',
  tools: [deleteFile],
})

export function fetch(request: Request) {
  return server.fetch(request)
}

requestInput returns the string that the user sends.

If the user declines or cancels, requestInput throws an Error. The tool call then ends with a tool error.

Spec 2025 and spec 2026#

On spec 2025, requestInput waits on the open session. The same tool call then continues with the answer.

On spec 2026, the handler returns input_required. Then the client runs the tool again with the answer. On spec 2026, the code before requestInput runs on each call, so it can run more than once.

If the work must run once, put that work after requestInput returns.

On spec 2026, a tool asks one question per call. A second requestInput in the same call throws an Error. To ask two questions, use two tools.

A TanStack chat() host pauses on input_required and shows the request to the user. MCP Client Input shows how the user answers.

requestInput does not work in an execution: 'task' tool. MCP Server Tasks has the details.

If the user sends yes, the tool returns Deleted plus the file path.