diff --git a/agent/tools/definitions.py b/agent/tools/definitions.py
index 0a91c33..29788cf 100644
--- a/agent/tools/definitions.py
+++ b/agent/tools/definitions.py
@@ -5,12 +5,16 @@
 
 from typing import Any
 
+MAX_STRICT_TOOLS = 20  # the Claude API refuses a request with more strict tools than this
+
 
 def _tool(name: str, description: str, **properties: dict[str, Any]) -> dict[str, Any]:
+    """Strict only when it takes inputs: strict checks the inputs, and the API allows at most
+    MAX_STRICT_TOOLS strict tools per request."""
     return {
         "name": name,
         "description": description,
-        "strict": True,
+        "strict": bool(properties),
         "input_schema": {
             "type": "object",
             "properties": properties,
diff --git a/tests/test_tool_definitions.py b/tests/test_tool_definitions.py
new file mode 100644
index 0000000..98cebed
--- /dev/null
+++ b/tests/test_tool_definitions.py
@@ -0,0 +1,12 @@
+"""The agent's tools are a request the Claude API accepts: on 2026-10-14 a 21st strict tool made
+every session fail with 'Too many strict tools'."""
+
+from agent.tools.definitions import MAX_STRICT_TOOLS, TOOLS
+
+
+def test_no_more_strict_tools_than_the_api_accepts():
+    assert sum(1 for t in TOOLS if t["strict"]) <= MAX_STRICT_TOOLS
+
+
+def test_every_tool_with_inputs_is_strict():
+    assert all(t["strict"] for t in TOOLS if t["input_schema"]["properties"])