[bugf][agent][tools=[] enables the deferred-tool machinery it has nothing to search]

exists() is 'is not None', so exists([]) is True and an empty tools list
counted as having tools. An agent built with tools=[] was given the
tool_search schema and DYNAMIC_TOOLS_NOTICE in its system prompt, then
advertised a tool whose catalog is empty on every request.

tools=None produced the correct empty result, so the two spellings of 'no
tools' behaved differently. CLAUDE.md documented the difference as a footgun
to avoid; the warning goes away with the cause.

Truthiness at the two call sites. mcp_enabled and max_loops='auto' still
enable deferral on their own, so an autonomous agent with no tools keeps the
loader it needs.

Author: ayaangazali

CLAUDE.md

@@ -1086,8 +1086,6 @@ from swarms import Agent
 
 **Don't instantiate heavyweight structures inside tight loops** — create agents and workflows once, reuse them across calls.
 
-**Don't pass `tools=[]` (empty list)** — pass `tools=None` instead. An empty list can confuse schema generation.
-
 **Don't use `streaming_on=True` and `streaming_callback` together on the same agent** — `streaming_on` streams to stdout; `streaming_callback` streams to your function. Pick one.
 
 **Don't set `context_compression=False` on very long autonomous sessions** — without compression the agent will eventually hit the context limit and raise an error.

swarms/structs/agent.py

@@ -676,8 +676,11 @@ def __init__(
                 self.system_prompt += "\n\n" + handoff_prompt
 
         # One condition so the notice cannot diverge from the loader.
+        # Truthiness, not exists(): exists() is `is not None`, so tools=[]
+        # counted as having tools and bought an empty agent the tool_search
+        # schema plus the notice in every prompt.
         defers_tools = self.dynamic_tools and (
-            exists(self.tools)
+            bool(self.tools)
             or self.mcp_enabled
             or self.max_loops == "auto"
         )
@@ -686,7 +689,7 @@ def __init__(
         if defers_tools:
             self.system_prompt += DYNAMIC_TOOLS_NOTICE
             self.setup_dynamic_tools()
-        elif exists(self.tools):
+        elif self.tools:
             self.tool_handling()
 
         if self.llm is None:

tests/structs/test_agent.py

@@ -3311,6 +3311,50 @@ def test_mismatched_lengths_raise_instead_of_dropping_tasks(self):
                 )
 
 
+class TestEmptyToolsList:
+    """`tools=[]` must mean the same as `tools=None`.
+
+    `exists()` is `is not None`, so an empty list counted as having tools:
+    the agent was given the `tool_search` schema it had nothing to search and
+    DYNAMIC_TOOLS_NOTICE in every prompt.
+    """
+
+    @staticmethod
+    def _agent(**kwargs):
+        return Agent(
+            agent_name="empty_tools_agent",
+            model_name="gpt-4o-mini",
+            max_loops=1,
+            **kwargs,
+        )
+
+    def test_empty_list_advertises_no_tools(self):
+        assert self._agent(tools=[]).tools_list_dictionary == []
+
+    def test_empty_list_matches_none(self):
+        empty = self._agent(tools=[])
+        none = self._agent(tools=None)
+        assert (
+            empty.tools_list_dictionary == none.tools_list_dictionary
+        )
+        assert ("tool_search" in empty.system_prompt) == (
+            "tool_search" in none.system_prompt
+        )
+
+    def test_a_real_tool_still_defers(self):
+        def sample(x: str) -> str:
+            """Return x.
+
+            Args:
+                x: anything
+            """
+            return x
+
+        agent = self._agent(tools=[sample])
+        assert agent.tools_list_dictionary
+        assert "tool_search" in agent.system_prompt
+
+
 if __name__ == "__main__":
     # Run all tests
     results = run_all_tests()