diff --git a/packages/opentelemetry-instrumentation-langchain/opentelemetry/instrumentation/langchain/span_utils.py b/packages/opentelemetry-instrumentation-langchain/opentelemetry/instrumentation/langchain/span_utils.py
index 09d365daaf..92e99b2a90 100644
--- a/packages/opentelemetry-instrumentation-langchain/opentelemetry/instrumentation/langchain/span_utils.py
+++ b/packages/opentelemetry-instrumentation-langchain/opentelemetry/instrumentation/langchain/span_utils.py
@@ -195,7 +195,10 @@ def set_request_params(span, kwargs, span_holder: SpanHolder):
         tool_defs = []
         for tool in tools:
             tool_function = tool.get("function", tool)
-            tool_def = {"name": tool_function.get("name")}
+            tool_def = {
+                "type": tool.get("type") or "function",
+                "name": tool_function.get("name"),
+            }
             if tool_function.get("description"):
                 tool_def["description"] = tool_function.get("description")
             params_val = tool_function.get("parameters", tool.get("input_schema"))
@@ -248,7 +251,10 @@ def set_chat_request(
         if functions:
             tool_defs = []
             for function in functions:
-                tool_def = {"name": function.get("name")}
+                tool_def = {
+                    "type": "function",
+                    "name": function.get("name"),
+                }
                 if function.get("description"):
                     tool_def["description"] = function.get("description")
                 if function.get("parameters"):
diff --git a/packages/opentelemetry-instrumentation-langchain/tests/test_tool_definitions.py b/packages/opentelemetry-instrumentation-langchain/tests/test_tool_definitions.py
new file mode 100644
index 0000000000..cdb0126404
--- /dev/null
+++ b/packages/opentelemetry-instrumentation-langchain/tests/test_tool_definitions.py
@@ -0,0 +1,94 @@
+import json
+from unittest.mock import Mock, patch
+
+from opentelemetry.instrumentation.langchain.span_utils import (
+    set_chat_request,
+    set_request_params,
+)
+from opentelemetry.semconv._incubating.attributes import (
+    gen_ai_attributes as GenAIAttributes,
+)
+
+
+def _span_attributes(span: Mock) -> dict:
+    return {call.args[0]: call.args[1] for call in span.set_attribute.call_args_list}
+
+
+def test_tool_definitions_preserve_source_type():
+    span = Mock()
+    span.is_recording.return_value = True
+    span_holder = Mock()
+    kwargs = {
+        "invocation_params": {
+            "tools": [
+                {
+                    "type": "custom_tool",
+                    "function": {
+                        "name": "get_weather",
+                        "description": "Get the weather",
+                        "parameters": {"type": "object"},
+                    },
+                }
+            ]
+        }
+    }
+
+    set_request_params(span, kwargs, span_holder)
+
+    tool_definitions = json.loads(_span_attributes(span)[GenAIAttributes.GEN_AI_TOOL_DEFINITIONS])
+    assert tool_definitions == [
+        {
+            "type": "custom_tool",
+            "name": "get_weather",
+            "description": "Get the weather",
+            "parameters": {"type": "object"},
+        }
+    ]
+
+
+def test_tool_definitions_default_to_function_type():
+    span = Mock()
+    span.is_recording.return_value = True
+    span_holder = Mock()
+    kwargs = {
+        "invocation_params": {
+            "tools": [
+                {
+                    "name": "get_weather",
+                    "description": "Get the weather",
+                    "input_schema": {"type": "object"},
+                }
+            ]
+        }
+    }
+
+    set_request_params(span, kwargs, span_holder)
+
+    tool_definitions = json.loads(_span_attributes(span)[GenAIAttributes.GEN_AI_TOOL_DEFINITIONS])
+    assert tool_definitions[0]["type"] == "function"
+
+
+def test_legacy_function_definitions_include_function_type():
+    span = Mock()
+    span.is_recording.return_value = True
+    span_holder = Mock()
+    kwargs = {
+        "invocation_params": {
+            "functions": [
+                {
+                    "name": "get_weather",
+                    "description": "Get the weather",
+                    "parameters": {"type": "object"},
+                }
+            ]
+        }
+    }
+
+    with patch(
+        "opentelemetry.instrumentation.langchain.span_utils.should_send_prompts",
+        return_value=True,
+    ):
+        set_chat_request(span, {}, [], kwargs, span_holder)
+
+    tool_definitions = json.loads(_span_attributes(span)[GenAIAttributes.GEN_AI_TOOL_DEFINITIONS])
+    assert tool_definitions[0]["type"] == "function"