Feature request: Support for server hosted tool calling and results

[bilyana-ilieva]

Hi,

Our custom Responses-API-compatible backend executes some tool calls server-side and streams them back using a custom item type prefixed with its implementor slug (e.g. implementor_slug:function_call) — following the Open Responses spec's extensibility guidelines for hosted tools and extended item types.

We have implemented a concept which intercepts these events at the fetch/stream layer and rewrites them in-flight to look like standard mcp_call items (with the real packet stashed under a hidden carrier key), so the existing MCP UI/parsing/history-replay code paths handle them with zero new frontend work. Wiring lives in packages/api/src/agents/run.ts: it's only activated when an agent's baseURL matches MY_API_INTERNAL_BASE_URL and useResponsesApi: true.

Will this enhancement be valuable to other contributors?
Is it planned that LibreChat will eventually support server hosted tool calling and results?

Thanks in advance!