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Merged
adwsingh merged 1 commit into from
Jun 11, 2025
Merged

Handle types we coerce to Strings in MCP #765

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70 changes: 64 additions & 6 deletions mcp/mcp-server/src/main/java/software/amazon/smithy/java/mcp/server/McpServer.java
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Original file line number Diff line number Diff line change
Expand Up @@ -9,6 +9,8 @@
import java.io.OutputStream;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.math.BigDecimal;
import java.math.BigInteger;
import java.nio.charset.StandardCharsets;
import java.util.ArrayList;
import java.util.HashMap;
Expand Down Expand Up @@ -155,9 +157,9 @@ private void handleRequest(JsonRpcRequest req) {
} else {
// Handle locally
var operation = tool.operation();
var input = req.getParams()
.getMember("arguments")
.asShape(operation.getApiOperation().inputBuilder());
var argumentsDoc = req.getParams().getMember("arguments");
var adaptedDoc = adaptDocument(argumentsDoc, operation.getApiOperation().inputSchema());
var input = adaptedDoc.asShape(operation.getApiOperation().inputBuilder());
var output = operation.function().apply(input, null);
var result = CallToolResult.builder()
.content(List.of(TextContent.builder()
Expand Down Expand Up @@ -417,14 +419,14 @@ public void awaitCompletion() throws InterruptedException {
done.await();
}

private record Tool(ToolInfo toolInfo, Operation operation, McpServerProxy proxy) {
private record Tool(ToolInfo toolInfo, Operation operation, McpServerProxy proxy, boolean requiredAdapting) {

Tool(ToolInfo toolInfo, Operation operation) {
this(toolInfo, operation, null);
this(toolInfo, operation, null, false);
}

Tool(ToolInfo toolInfo, McpServerProxy proxy) {
this(toolInfo, null, proxy);
this(toolInfo, null, proxy, false);
}
}

Expand All @@ -436,6 +438,62 @@ private static String appendSentences(String first, String second) {
return first + second;
}

private static Document adaptDocument(Document doc, Schema schema) {
var fromType = doc.type();
var toType = schema.type();
return switch (toType) {
case BIG_DECIMAL -> switch (fromType) {
case STRING -> Document.of(new BigDecimal(doc.asString()));
case BIG_INTEGER -> doc;
default -> badType(fromType, toType);
};
case BIG_INTEGER ->
switch (fromType) {
case STRING -> Document.of(new BigInteger(doc.asString()));
case BIG_INTEGER -> doc;
default -> badType(fromType, toType);
};
case BLOB -> switch (fromType) {
case STRING -> Document.of(doc.asString().getBytes(StandardCharsets.UTF_8));
case BLOB -> doc;
default -> badType(fromType, toType);
};
case STRUCTURE, UNION -> {
var convertedMembers = new HashMap<String, Document>();
var members = schema.members();
for (var member : members) {
var memberName = member.memberName();
var memberDoc = doc.getMember(memberName);
if (memberDoc != null) {
convertedMembers.put(memberName, adaptDocument(memberDoc, member.memberTarget()));
}
}
yield Document.of(convertedMembers);
}
case LIST, SET -> {
var listMember = schema.listMember();
var convertedList = new ArrayList<Document>();
for (var item : doc.asList()) {
convertedList.add(adaptDocument(item, listMember.memberTarget()));
}
yield Document.of(convertedList);
}
case MAP -> {
var mapValue = schema.mapValueMember();
var convertedMap = new HashMap<String, Document>();
for (var entry : doc.asStringMap().entrySet()) {
convertedMap.put(entry.getKey(), adaptDocument(entry.getValue(), mapValue.memberTarget()));
}
yield Document.of(convertedMap);
}
default -> doc;
};
}

private static Document badType(ShapeType from, ShapeType to) {
throw new RuntimeException("Cannot convert from " + from + " to " + to);
}

public static McpServerBuilder builder() {
return new McpServerBuilder();
}
Expand Down
146 changes: 146 additions & 0 deletions mcp/mcp-server/src/test/java/software/amazon/smithy/java/mcp/server/McpServerTest.java
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Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -6,13 +6,22 @@
package software.amazon.smithy.java.mcp.server;

import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertNotNull;
import static org.junit.jupiter.api.Assertions.assertTrue;

import java.math.BigDecimal;
import java.math.BigInteger;
import java.nio.charset.StandardCharsets;
import java.util.List;
import java.util.Map;
import java.util.concurrent.atomic.AtomicReference;
import org.junit.jupiter.api.AfterEach;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;
import software.amazon.smithy.java.client.core.interceptors.ClientInterceptor;
import software.amazon.smithy.java.client.core.interceptors.InputHook;
import software.amazon.smithy.java.core.serde.document.Document;
import software.amazon.smithy.java.dynamicschemas.StructDocument;
import software.amazon.smithy.java.json.JsonCodec;
import software.amazon.smithy.java.json.JsonSettings;
import software.amazon.smithy.java.mcp.model.JsonRpcRequest;
Expand All @@ -21,6 +30,7 @@
import software.amazon.smithy.java.server.Server;
import software.amazon.smithy.model.Model;
import software.amazon.smithy.model.shapes.ShapeId;
import software.amazon.smithy.model.shapes.ShapeType;

public class McpServerTest {
private static final JsonCodec CODEC = JsonCodec.builder()
Expand Down Expand Up @@ -84,6 +94,9 @@ public void validateToolStructure() {
var list = properties.get("list").asStringMap();
assertEquals("array", list.get("type").asString());

var bigDecimal = properties.get("bigDecimalField").asStringMap();
assertEquals("string", bigDecimal.get("type").asString());

var listItems = list.get("items").asStringMap();
assertEquals("object", listItems.get("type").asString());
var listItemProperties = listItems.get("properties").asStringMap();
Expand All @@ -106,6 +119,111 @@ public void validateToolStructure() {
validateNestedStructure(doubleNestedProperties);
}

@Test
void testInputAdaptation() {
AtomicReference<StructDocument> capturedInput = new AtomicReference<>();
server = McpServer.builder()
.input(input)
.output(output)
.addService(ProxyService.builder()
.service(ShapeId.from("smithy.test#TestService"))
.proxyEndpoint("http://localhost")
.clientConfigurator(
clientConfigurator -> clientConfigurator.addInterceptor(new ClientInterceptor() {
@Override
public void readBeforeSerialization(InputHook<?, ?> hook) {
capturedInput.set((StructDocument) hook.input());
}
}))
.model(MODEL)
.build())
.build();

server.start();

var bigDecimalValue = BigDecimal.valueOf(Integer.MAX_VALUE).add(BigDecimal.TEN);
var bigIntegerValue = BigInteger.valueOf(Long.MAX_VALUE).add(BigInteger.valueOf(100));
var blobValue = "Hello, World!";
var nestedBigDecimalValue = new BigDecimal("123.456");
var nestedBigIntegerValue = new BigInteger("9876543210");
var nestedBlobValue = "Nested blob content";

write("tools/call",
Document.of(
Map.of("name",
Document.of("TestOperation"),
"arguments",
Document.of(Map.of(
"bigDecimalField",
Document.of(bigDecimalValue.toString()),
"bigIntegerField",
Document.of(bigIntegerValue.toString()),
"blobField",
Document.of(blobValue),
"nestedWithBigNumbers",
Document.of(Map.of(
"nestedBigDecimal",
Document.of(nestedBigDecimalValue.toString()),
"nestedBigInteger",
Document.of(nestedBigIntegerValue.toString()),
"nestedBlob",
Document.of(nestedBlobValue),
"bigDecimalList",
Document.of(List.of(
Document.of("100.25"),
Document.of("200.75"))))))))));
assertNotNull(read());
var inputDocument = capturedInput.get();

var bigDecimalField = inputDocument.getMember("bigDecimalField");
assertNotNull(bigDecimalField);
assertEquals(ShapeType.BIG_DECIMAL, bigDecimalField.type());
assertEquals(bigDecimalValue, bigDecimalField.asBigDecimal());

var bigIntegerField = inputDocument.getMember("bigIntegerField");
assertNotNull(bigIntegerField);
assertEquals(ShapeType.BIG_INTEGER, bigIntegerField.type());
assertEquals(bigIntegerValue, bigIntegerField.asBigInteger());

var blobField = inputDocument.getMember("blobField");
assertNotNull(blobField);
assertEquals(ShapeType.BLOB, blobField.type());
assertEquals(blobValue, new String(blobField.asBlob().array(), StandardCharsets.UTF_8));

var nestedWithBigNumbers = inputDocument.getMember("nestedWithBigNumbers");
assertNotNull(nestedWithBigNumbers);
assertEquals(ShapeType.STRUCTURE, nestedWithBigNumbers.type());

var nestedStruct = (StructDocument) nestedWithBigNumbers;

var nestedBigDecimalField = nestedStruct.getMember("nestedBigDecimal");
assertNotNull(nestedBigDecimalField);
assertEquals(ShapeType.BIG_DECIMAL, nestedBigDecimalField.type());
assertEquals(nestedBigDecimalValue, nestedBigDecimalField.asBigDecimal());

var nestedBigIntegerField = nestedStruct.getMember("nestedBigInteger");
assertNotNull(nestedBigIntegerField);
assertEquals(ShapeType.BIG_INTEGER, nestedBigIntegerField.type());
assertEquals(nestedBigIntegerValue, nestedBigIntegerField.asBigInteger());

var nestedBlobField = nestedStruct.getMember("nestedBlob");
assertNotNull(nestedBlobField);
assertEquals(ShapeType.BLOB, nestedBlobField.type());
assertEquals(nestedBlobValue, new String(nestedBlobField.asBlob().array(), StandardCharsets.UTF_8));

var bigDecimalListField = nestedStruct.getMember("bigDecimalList");
assertNotNull(bigDecimalListField);
assertEquals(ShapeType.LIST, bigDecimalListField.type());
var bigDecimalList = bigDecimalListField.asList();
assertEquals(2, bigDecimalList.size());
assertEquals(ShapeType.BIG_DECIMAL, bigDecimalList.get(0).type());
assertEquals(ShapeType.BIG_DECIMAL, bigDecimalList.get(1).type());
assertEquals(new BigDecimal("100.25"), bigDecimalList.get(0).asBigDecimal());
assertEquals(new BigDecimal("200.75"), bigDecimalList.get(1).asBigDecimal());

server.shutdown().join();
}

private void validateNestedStructure(Map<String, Document> properties) {
var nestedStr = properties.get("nestedStr").asStringMap();
assertEquals("string", nestedStr.get("type").asString());
Expand Down Expand Up @@ -154,6 +272,7 @@ private JsonRpcResponse read() {
/// A TestOperation
operation TestOperation {
input: TestInput
output: TestInput
}

/// An input for TestOperation with a nested member
Expand All @@ -167,6 +286,14 @@ private JsonRpcResponse read() {
list: NestedList

doubleNestedList: DoubleNestedList

bigDecimalField: BigDecimal

bigIntegerField: BigInteger

blobField: Blob

nestedWithBigNumbers: NestedWithBigNumbers
}

list NestedList {
Expand All @@ -193,6 +320,25 @@ private JsonRpcResponse read() {
structure Recursive {
/// the nested field that points back to us
nested: Nested
}

/// A structure containing big number types
structure NestedWithBigNumbers {
/// A nested BigDecimal
nestedBigDecimal: BigDecimal

/// A nested BigInteger
nestedBigInteger: BigInteger

/// A nested Blob
nestedBlob: Blob

/// A list of BigDecimals
bigDecimalList: BigDecimalList
}

list BigDecimalList {
member: BigDecimal
}""";

private static final Model MODEL = Model.assembler()
Expand Down