Vercel AI SDK returns empty text after MCP tool call resolution

(edited)

When invoking a tool via experimental_createMCPClient() and generateText using the Vercel AI SDK, the final .text field in the response is always an empty string, even though the tool result contains valid data.

Issue replicates even with maxToolRoundtrips: 3 set.

"text": "",
  "files": [],
  "reasoningDetails": [],
  "toolCalls": [
    {
      "type": "tool-call",
      "toolCallId": "9COeKo3dUxyMgLea",
      "toolName": "get_l1_orderbook",
...

FYI Env

ai: 4.3.16

@ai-sdk/google: 1.2.19

bun: 1.2.16

Model: gemini-1.5-pro-latest

Tools: experimental_createMCPClient() (SSE-based)

Vercel Staff

Tool calls store their output in the tool result and won't usually have a .text field, unless you've explicitly requested it like "get the weather for London and return a summary"

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