Requests to vertex ai fail if z.record(z.string()) used in tool schema

[tjenkinson]

Description

See the code example below. When using vertex ai if z.record(z.string()) is used an error occurs because in the generated open api schema something becomes undefined

Code example

import { createVertex } from '@ai-sdk/google-vertex'
import { CoreMessage, Tool, generateText, tool, LanguageModelV1 } from 'ai'

const vertex = createVertex({
  project: ...,
  location: ...,
})

const gemini2Flash: LanguageModelV1 = vertex.languageModel(
  'gemini-2.0-flash-001',
)

await generateText({
  model: gemini2Flash,
  prompt: 'Hi',
  tools: {
    test: tool({
      description: 'Test',
      parameters: z.object({
        // the issue
        something: z.record(z.string())
      }),
    }
  }
})

AI provider

@ai-sdk/google-vertex 2.2.14

Additional context

I opened a PR to fix this here: #5626