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name: rollout-and-tools description: "Use when modifying verl rollout engines, multi-turn agent loops, function tools, tool schemas, rollout traces, or generation-server flows." disable-model-invocation: true metadata: disco-role: operating license: Apache 2.0

Rollout And Tools

Use this sub-skill when the task touches verl rollout behavior rather than trainer optimizer policy: rollout backend config, async generation servers, multi-turn agent loops, tool calling, function-tool schema authoring, tokenization sanity checks, trace output, or rollout visualization.

Route The Task

• For rollout backend choices and config fields, read Rollout workflows.
• For @function_tool, BaseTool, schema loading, and tool dispatch, read Tooling API.
• For tokenization warnings, tool parser issues, trace volume, and viewer pitfalls, read Troubleshooting.
• To preflight a Python file used by actor_rollout_ref.rollout.multi_turn.function_tool_path, run validate_function_tool.py.

Safe Defaults

• Prefer actor_rollout_ref.rollout.mode=async; sync rollout mode is removed.
• Use actor_rollout_ref.rollout.multi_turn.enable=True plus actor_rollout_ref.rollout.agent.default_agent_loop=tool_agent for built-in tool-calling loops.
• Use function tools for stateless fn(**parameters) calls; use native BaseTool tools for lifecycle, per-trajectory state, sandbox resources, or tools_kwargs.
• Keep tokenization_sanity_check_mode=strict until the model chat template has been validated; use ignore_strippable only for whitespace-only template drift.
• Treat rollout viewer as an interactive diagnostic over generated JSONL rollout data, not as a required runtime dependency.

Verification Targets

• CPU-safe candidates: function-tool registration/return tests, ToolAgentLoop._call_tool error-handling tests, Qwen3 parser safety tests, and vLLM CLI argument parsing tests.
• When changing multi-turn or tool parsing behavior, include a case where a malformed tool call returns a readable ToolResponse instead of crashing the loop.