Unable to integrate Mongodb mcp with google adk #3401

Describe the bug
When using MCPToolset with MongoDB MCP in an LlmAgent, some function parameters have enum values that are integers (e.g., [256, 512, 1024, ...]) while the schema specifies type: string. This causes google.genai.errors.ClientError: 400 INVALID_ARGUMENT when the agent is loaded or tools are called, with messages like:

Invalid value at 'tools[0].function_declarations[13].parameters.properties[2].value.items.any_of[1].properties[0].value.properties[7].value.properties[0].value.enum[0]' (TYPE_STRING), 256

To Reproduce
Steps to reproduce the behavior:

1. Install the latest google-adk and 'MongoDB mcp server'
2. Start the MongoDB MCP server before running the agent:

npx -y mongodb-mcp-server \
  --connectionString "mongodb://localhost:27018?directConnection=true" \
  --transport http \
  --httpHost=0.0.0.0 \
  --httpPort=8080

3. Create an agent using MongoDB MCP:

from google.adk.agents import LlmAgent
from google.adk.tools.mcp_tool import MCPToolset, StreamableHTTPConnectionParams

mcp_server_url = "http://127.0.0.1:8080/mcp"

root_agent = LlmAgent(
    model="gemini-2.5-flash",
    name="mongo_mcp_agent",
    instruction="Help with MongoDB data access",
    tools=[MCPToolset(connection_params=StreamableHTTPConnectionParams(url=mcp_server_url))]
)

4. Run adk web . from the agent folder.
5. Observe errors related to TYPE_STRING and enum integer values.

Expected behavior
Integer enum values returned by MongoDB MCP should either:

• Be automatically cast to strings when the schema type is string, or
• The schema itself should use type: integer, so ADK can validate properly.

Desktop

• OS: macOS 13.5
• Python version: 3.13
• ADK version: [latest]

Model Information:

• Using LiteLLM: No
• Model: gemini-2.5-flash

Additional context
This breaks integration of MongoDB MCP with LlmAgent in ADK. Guidance on proper schema handling or automatic enum type normalization is needed.