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Fail fast when tool is missing input_schema in function calling #4779

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Fail fast when tool is missing input_schema in function calling #4779

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07c7e88
Fix function calling payload for tools without input_schema
ohltyler Apr 4, 2026
a5cbfb0
Improve test coverage for default input_schema fallback
ohltyler Apr 6, 2026
7b8e6c5
Extract input_schema key and default value into constants
ohltyler Apr 7, 2026
3fa81f5
Replace default input_schema fallback with clear error
ohltyler Apr 8, 2026
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3 changes: 3 additions & 0 deletions ml-algorithms/src/main/java/org/opensearch/ml/engine/algorithms/agent/AgentUtils.java
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Original file line number Diff line number Diff line change
Expand Up @@ -240,6 +240,9 @@ public static String addToolsToFunctionCalling(
toolParams.put(NAME, StringEscapeUtils.escapeJson(tool.getName()));
toolParams.put(DESCRIPTION, StringEscapeUtils.escapeJson(tool.getDescription()));
Map<String, ?> attributes = tool.getAttributes();
if (attributes == null || !attributes.containsKey("input_schema")) {
toolParams.put("attributes.input_schema", "{\"type\":\"object\",\"properties\":{}}");
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@owaiskazi19 owaiskazi19 Apr 6, 2026

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Can we create constants for both key and value

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@ohltyler ohltyler Apr 7, 2026

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Done — extracted both into INPUT_SCHEMA and DEFAULT_INPUT_SCHEMA constants, and replaced all 5 occurrences of the "input_schema" string literal in the file.

}
if (attributes != null) {
for (String key : attributes.keySet()) {
toolParams.put("attributes." + key, attributes.get(key));
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44 changes: 44 additions & 0 deletions ml-algorithms/src/test/java/org/opensearch/ml/engine/algorithms/agent/AgentUtilsTest.java
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Expand Up @@ -1252,6 +1252,50 @@ public void testAddToolsToFunctionCalling() {
assertEquals(expectedTools, parameters.get(TOOLS));
}

@Test
public void testAddToolsToFunctionCalling_ToolWithNoInputSchema() {
Tool toolNoSchema = mock(Tool.class);
when(toolNoSchema.getName()).thenReturn("VectorDBTool");
when(toolNoSchema.getDescription()).thenReturn("knn dense retrieval tool");
when(toolNoSchema.getAttributes()).thenReturn(null);

Map<String, Tool> tools = new HashMap<>();
tools.put("VectorDBTool", toolNoSchema);

Map<String, String> parameters = new HashMap<>();
String toolTemplate =
"{\"toolSpec\":{\"name\":\"${tool.name}\",\"description\":\"${tool.description}\",\"inputSchema\":{\"json\":${tool.attributes.input_schema}}}}";
parameters.put(TOOL_TEMPLATE, toolTemplate);

AgentUtils.addToolsToFunctionCalling(tools, parameters, List.of("VectorDBTool"), "prompt");

String result = parameters.get(TOOLS);
Assert.assertFalse(result.contains("${tool.attributes.input_schema}"));
Assert.assertTrue(result.contains("\"inputSchema\":{\"json\":{\"type\":\"object\",\"properties\":{}}}"));
}

@Test
public void testAddToolsToFunctionCalling_ToolWithAttributesButNoInputSchema() {
Tool toolNoSchema = mock(Tool.class);
when(toolNoSchema.getName()).thenReturn("VectorDBTool");
when(toolNoSchema.getDescription()).thenReturn("knn dense retrieval tool");
when(toolNoSchema.getAttributes()).thenReturn(Map.of("some_other_key", "value"));

Map<String, Tool> tools = new HashMap<>();
tools.put("VectorDBTool", toolNoSchema);

Map<String, String> parameters = new HashMap<>();
String toolTemplate =
"{\"toolSpec\":{\"name\":\"${tool.name}\",\"description\":\"${tool.description}\",\"inputSchema\":{\"json\":${tool.attributes.input_schema}}}}";
parameters.put(TOOL_TEMPLATE, toolTemplate);

AgentUtils.addToolsToFunctionCalling(tools, parameters, List.of("VectorDBTool"), "prompt");

String result = parameters.get(TOOLS);
Assert.assertFalse(result.contains("${tool.attributes.input_schema}"));
Assert.assertTrue(result.contains("\"inputSchema\":{\"json\":{\"type\":\"object\",\"properties\":{}}}"));
}

@Test
public void testAddToolsToFunctionCalling_ToolNotRegistered() {
Map<String, Tool> tools = new HashMap<>();
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