feat(snowflake): add function calling support for Snowflake Cortex REST API

[jatorre]

Summary

Adds function calling (tools) support for Snowflake Cortex REST API, enabling tool use with models like Claude 3.5 Sonnet.

Changes

Implementation (litellm/llms/snowflake/chat/transformation.py)

• ✅ Add tools and tool_choice to supported OpenAI parameters
• ✅ Implement request transformation: OpenAI → Snowflake tool_spec format
• ✅ Implement response transformation: Snowflake content_list → OpenAI tool_calls
• ✅ Add tool_choice transformation to Snowflake's array format

Testing

• ✅ 7 unit tests for request/response transformations (tests/test_litellm/llms/snowflake/chat/test_snowflake_chat_transformation.py)
• ✅ Integration test for Responses API with tool calling (tests/llm_translation/test_snowflake.py)
• ✅ All tests passing

Technical Details

Request Transformations

Tools: OpenAI format → Snowflake tool_spec

# Before (OpenAI)
{"type": "function", "function": {"name": "get_weather", "parameters": {...}}}

# After (Snowflake)
{"tool_spec": {"type": "generic", "name": "get_weather", "input_schema": {...}}}

Tool Choice: OpenAI nested → Snowflake array

# Before (OpenAI)
{"type": "function", "function": {"name": "get_weather"}}

# After (Snowflake)
{"type": "tool", "name": ["get_weather"]}

Response Transformations

Parses Snowflake's unique format:

{
  "content_list": [
    {"type": "tool_use", "tool_use": {"tool_use_id": "...", "name": "...", "input": {...}}}
  ]
}

Converts to OpenAI format:

{
  "content": "...",
  "tool_calls": [{"id": "...", "type": "function", "function": {"name": "...", "arguments": "..."}}]
}

Verification

Tested with real Snowflake Cortex API (account: XXXXXX):

• ✅ Tool calls with tool_choice (forced tool use)
• ✅ Tool calls in auto mode (model decides)
• ✅ Mixed text + tool call responses
• ✅ Proper JSON argument serialization
• ✅ Works with both completion() and responses() APIs

Example output:

Tool name: get_weather
Arguments: {"location": "Paris, France"}

Context

• Snowflake added function calling support to their REST API after the initial LiteLLM integration (PR [FEAT] Support for Snowflake REST API LLMs #7979 #8950, merged March 2025)
• Currently only supported on specific models: Claude 3.5 Sonnet, Claude 3.7 Sonnet, Claude 4 Sonnet
• Official docs: https://docs.snowflake.com/en/user-guide/snowflake-cortex/cortex-llm-rest-api
• Closes [Bug/Feature]: Snowflake Cortex now supports function calling but LiteLLM doesn't expose it #15218

Test Plan

Unit tests (run automatically in CI):

pytest tests/test_litellm/llms/snowflake/chat/test_snowflake_chat_transformation.py -v

Integration test (requires Snowflake credentials - marked as skip):

# Set credentials first:
export SNOWFLAKE_JWT="your-jwt-token"
export SNOWFLAKE_ACCOUNT_ID="your-account-id"

# Then run:
pytest tests/llm_translation/test_snowflake.py::test_snowflake_tool_calling_responses_api -s

Breaking Changes

None - This is purely additive functionality.

🤖 Generated with Claude Code

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