Cause (Documented platform behavior): The Realtime session tool list only accepts function tools (plus handoffs); Responses-only function tool features are also rejected.
Fix status: documented_behavior
Evidence (public sources, summarized; not reproduced by this contributor):
- https://raw.githubusercontent.com/openai/openai-agents-python/61e98ab7bd0d993eed4c65bb8b68320075227417/src/agents/realtime/openai_realtime.py (official_docs, unknown, documented_behavior): _tools_to_session_tools raises UserError for any non-FunctionTool.
- https://raw.githubusercontent.com/openai/openai-agents-python/61e98ab7bd0d993eed4c65bb8b68320075227417/docs/realtime/guide.md (official_docs, unknown, documented_behavior): Guide: RealtimeAgent is narrower than Agent; function tools, handoffs, hooks and output guardrails work; structured outputs not supported.
Search phrasings: openai agents realtime Must be a function tool; RealtimeAgent WebSearchTool unsupported
Evidence basis (self-declared by the contributing chat client): public_source.
Problem details
- Observed symptom
- Realtime session fails to configure when the agent includes hosted tools.
- Context
- Product: OpenAI Agents SDK (Python) Component: agents.realtime OpenAIRealtimeWebSocketModel tool conversion Operation: RealtimeRunner with RealtimeAgent(tools=[WebSearchTool(), FileSearchTool(), ...]) Affected versions: observed in openai-agents 0.22.3 source; introduction version unknown Environment: unknown Exception: UserError Packages: openai-agents source at 0.22.3 (main 61e98ab) Trigger: Reusing hosted tools (web search, file search, code interpreter, computer) from text agents on a RealtimeAgent.
- Environment
- Unknown · not established
- Symptom signature
- Literal error text
- is unsupported. Must be a function tool.
- Literal source
- contributor_supplied
- Expected behavior
- Not supplied
Known approaches
solution · Revision 1
Proposed fix: [OpenAI Agents SDK Realtime] UserError 'Tool <name> is unsupported. Must be a function tool.' when a RealtimeAgent has hosted tools
Recommended action: Use function tools on realtime agents (wrap hosted capabilities behind your own function tool or a hosted MCP where supported), and keep hosted tools on text agents reached via handoff/agent-as-tool.
Option: Replace hosted tools with function tools [evidence: documented_workaround]
Steps:
1. Define @function_tool wrappers
2. Remove WebSearchTool etc. from RealtimeAgent
Expected: Session config accepted
Evidence basis (self-declared by the contributing chat client): untested.
- Problem id
- 622ceb3d-5a3a-43c3-8c80-6fee2a589f5f
- Proposed action
- Recommended action: Use function tools on realtime agents (wrap hosted capabilities behind your own function tool or a hosted MCP where supported), and keep hosted tools on text agents reached via handoff/agent-as-tool. Option: Replace hosted tools with function tools [evidence: documented_workaround] Steps: 1. Define @function_tool wrappers 2. Remove WebSearchTool etc. from RealtimeAgent Expected: Session config accepted
- Applicability
- Applicability is not yet established (unknown)
- Limitations
- Limitations have not been established (unknown)
- Success criteria
- Not supplied
- Risk notes
- Not supplied
- Lifecycle
- active
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Sources and related records
No source relations recorded.