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refactor: fix the return format of CallToolResult #68

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refactor: fix the return format of CallToolResult #68

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5dbad11
refactor: fix the return format of CallToolResult
TheEterna Oct 4, 2025
702a47f
test: "Modify the test cases according to the MCP protocol
TheEterna Oct 4, 2025
fb4022e
test: "Modify the test cases according to the MCP protocol
TheEterna Oct 4, 2025
d8137f5
Merge branch 'refactor/issue-67-Update-the-AbstractMcpToolMethodCallb…
TheEterna Oct 4, 2025
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36 changes: 24 additions & 12 deletions ...ns/src/main/java/org/springaicommunity/mcp/method/tool/AbstractMcpToolMethodCallback.java
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Original file line number Diff line number Diff line change
Expand Up @@ -23,8 +23,8 @@
import java.util.Objects;
import java.util.stream.Stream;

import io.modelcontextprotocol.spec.McpSchema.CallToolRequest;
import io.modelcontextprotocol.spec.McpSchema.CallToolResult;
import io.modelcontextprotocol.spec.McpSchema.*;
import io.modelcontextprotocol.spec.McpSchema.CallToolResult.*;
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Avoid wildcards

import org.springaicommunity.mcp.annotation.McpMeta;
import org.springaicommunity.mcp.annotation.McpProgressToken;
import org.springaicommunity.mcp.annotation.McpTool;
Expand Down Expand Up @@ -144,36 +144,48 @@ protected Object buildTypedArgument(Object value, Type type) {
* @return A CallToolResult representing the processed result
*/
protected CallToolResult convertValueToCallToolResult(Object result) {
Builder callToolResultBuilder = CallToolResult.builder();

// According to the MCP protocol For backwards compatibility, a tool that returns
// structured content SHOULD also return the serialized JSON in a TextContent
// block.
if (this.returnMode == ReturnMode.STRUCTURED) {
String jsonOutput = JsonParser.toJson(result);
Object structuredOutput = JsonParser.fromJson(jsonOutput, Object.class);
callToolResultBuilder.structuredContent(structuredOutput);
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The structured content is available only to JSON so you can do that :

return CallToolResult.builder().structuredContent(structuredOutput).addTextContent(jsonOutput).build();

}

// Return the result if it's already a CallToolResult
if (result instanceof CallToolResult) {
return (CallToolResult) result;
}
else if (result instanceof TextContent textContent) {
// Structured content is only supported in TextContent
return callToolResultBuilder.addContent(textContent).isError(false).meta(null).build();
}
else if (result instanceof Content content) {
return CallToolResult.builder().addContent(content).isError(false).meta(null).build();
}

Type returnType = this.toolMethod.getGenericReturnType();

if (returnMode == ReturnMode.VOID || returnType == Void.TYPE || returnType == void.class) {
return CallToolResult.builder().addTextContent(JsonParser.toJson("Done")).build();
}

if (this.returnMode == ReturnMode.STRUCTURED) {
String jsonOutput = JsonParser.toJson(result);
Object structuredOutput = JsonParser.fromJson(jsonOutput, Object.class);
return CallToolResult.builder().structuredContent(structuredOutput).build();
return callToolResultBuilder.addTextContent(JsonParser.toJson("Done")).build();
}

// Default to text output
if (result == null) {
return CallToolResult.builder().addTextContent("null").build();
return callToolResultBuilder.addTextContent("null").build();
}

// For string results in TEXT mode, return the string directly without JSON
// serialization
if (result instanceof String) {
return CallToolResult.builder().addTextContent((String) result).build();
return callToolResultBuilder.addTextContent((String) result).build();
}

// For other types, serialize to JSON
return CallToolResult.builder().addTextContent(JsonParser.toJson(result)).build();
return callToolResultBuilder.addTextContent(JsonParser.toJson(result)).build();
}

/**
Expand Down
4 changes: 2 additions & 2 deletions ...nnotations/src/main/java/org/springaicommunity/mcp/provider/tool/SyncMcpToolProvider.java
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Original file line number Diff line number Diff line change
Expand Up @@ -120,9 +120,9 @@ public List<SyncToolSpecification> getToolSpecifications() {

var tool = toolBuilder.build();

boolean useStructuredOtput = tool.outputSchema() != null;
boolean useStructuredOutput = tool.outputSchema() != null;

ReturnMode returnMode = useStructuredOtput ? ReturnMode.STRUCTURED
ReturnMode returnMode = useStructuredOutput ? ReturnMode.STRUCTURED
: (methodReturnType == Void.TYPE || methodReturnType == void.class ? ReturnMode.VOID
: ReturnMode.TEXT);

Expand Down
1 change: 0 additions & 1 deletion .../src/test/java/org/springaicommunity/mcp/method/tool/AsyncMcpToolMethodCallbackTests.java
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Expand Up @@ -567,7 +567,6 @@ public void testMonoToolReturningComplexObject() throws Exception {
StepVerifier.create(callback.apply(exchange, request)).assertNext(result -> {
assertThat(result).isNotNull();
assertThat(result.isError()).isFalse();
assertThat(result.content()).isEmpty();
assertThat(result.structuredContent()).isNotNull();
assertThat((Map<String, Object>) result.structuredContent()).containsEntry("name", "test");
assertThat((Map<String, Object>) result.structuredContent()).containsEntry("value", 42);
Expand Down
1 change: 0 additions & 1 deletion .../java/org/springaicommunity/mcp/method/tool/AsyncStatelessMcpToolMethodCallbackTests.java
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Original file line number Diff line number Diff line change
Expand Up @@ -603,7 +603,6 @@ public void testMonoToolReturningComplexObject() throws Exception {
StepVerifier.create(callback.apply(context, request)).assertNext(result -> {
assertThat(result).isNotNull();
assertThat(result.isError()).isFalse();
assertThat(result.content()).isEmpty();
assertThat(result.structuredContent()).isNotNull();
assertThat((Map<String, Object>) result.structuredContent()).containsEntry("name", "test");
assertThat((Map<String, Object>) result.structuredContent()).containsEntry("value", 42);
Expand Down
1 change: 0 additions & 1 deletion ...s/src/test/java/org/springaicommunity/mcp/method/tool/SyncMcpToolMethodCallbackTests.java
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Expand Up @@ -514,7 +514,6 @@ public void testToolReturningComplexObject() throws Exception {
assertThat(result.isError()).isFalse();
// For complex return types (non-primitive, non-wrapper, non-CallToolResult),
// the new implementation should return structured content
assertThat(result.content()).isEmpty();
assertThat(result.structuredContent()).isNotNull();
assertThat((Map<String, Object>) result.structuredContent()).containsEntry("name", "test");
assertThat((Map<String, Object>) result.structuredContent()).containsEntry("value", 42);
Expand Down
1 change: 0 additions & 1 deletion ...t/java/org/springaicommunity/mcp/method/tool/SyncStatelessMcpToolMethodCallbackTests.java
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Original file line number Diff line number Diff line change
Expand Up @@ -543,7 +543,6 @@ public void testToolReturningComplexObject() throws Exception {
assertThat(result.isError()).isFalse();
// For complex return types (non-primitive, non-wrapper, non-CallToolResult),
// the new implementation should return structured content
assertThat(result.content()).isEmpty();
assertThat(result.structuredContent()).isNotNull();
assertThat((Map<String, Object>) result.structuredContent()).containsEntry("name", "test");
assertThat((Map<String, Object>) result.structuredContent()).containsEntry("value", 42);
Expand Down