RestApiTool crashes on a request body media type that has no schema #7838

🔴 Required Information

Describe the Bug:
A RestApiTool whose request body declares a media type without a schema (OpenAPI allows content: {application/octet-stream: {}}) crashes when called:

AttributeError: 'NoneType' object has no attribute 'type'

OperationParser handles this case: it normalizes the schema with _schema_from_openapi, where None becomes Schema(), and exposes a single body parameter. RestApiTool._prepare_request_params then reads media_type_object.schema_ raw and calls .type on None. So the tool is generated and offered to the model, but every call fails. mypy already reports these lines (Item "None" of "Schema | Reference | Any | None" has no attribute "type").

Steps to Reproduce:

op = Operation(
    operationId="upload_contract",
    requestBody=RequestBody(content={"application/octet-stream": MediaType()}),
)
params = OperationParser(op).get_parameters()   # [body]
tool = RestApiTool(name="upload_contract", description="...", endpoint=..., operation=op)
tool._prepare_request_params(params, {"body": b"%PDF-1.7"})

Expected Behavior:
The bytes are sent as the request body with Content-Type: application/octet-stream.

Observed Behavior:
AttributeError: 'NoneType' object has no attribute 'type'

Environment Details:

• ADK Library Version (pip show google-adk): 2.13.0 (also on main at 75fb788)
• Desktop OS: macOS
• Python Version (python -V): 3.11.16

Model Information:

• Are you using LiteLLM: No
• Which model is being used: N/A (tool request building)

🟡 Optional Information

How often has this issue occurred?:

• Always (100%), for request bodies whose media type has no schema