@tanstack/ai-mcp/src/server/output.ts

Host-side Model Context Protocol client for TanStack AI: discover and run MCP server tools, resources, and prompts in any adapter's chat() loop, with generated end-to-end types.

import { validateWithStandardSchema } from '@tanstack/ai'

/**
 * Internal. Parses a tool output with its `outputSchema`, like chat() does,
 * so the result matches the advertised output view. A result that fails
 * the schema but that the tool built itself (`isOwnResult`) is kept.
 * This module loads no MCP SDK, so the direct client can use it.
 */
export async function parseToolOutput(
  tool: { name: string; outputSchema?: unknown },
  output: unknown,
  isOwnResult: (value: unknown) => boolean,
) {
  const parsed = await validateWithStandardSchema(tool.outputSchema, output)
  if (parsed.success) return parsed.data
  if (isOwnResult(output)) return output
  const issues = parsed.issues.map((issue) => issue.message).join(', ')
  throw new Error(
    `Tool ${tool.name} returned output that does not match its outputSchema: ${issues}`,
  )
}