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fix: Remove JsonSchema and use a Map for inputSchema to support json schemas dialect #749

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fix: Remove JsonSchema and use a Map for inputSchema to support json schemas dialect #749

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6b0a8ee
feat: remove JsonSchema an use a Map for inputSchema
bilaloumehdi Jan 13, 2026
26ecf80
test: add test for a schema contains oneof
bilaloumehdi Jan 14, 2026
1fdc258
Merge branch 'main' into fix/json-schema-spec-support
bilaloumehdi Jan 20, 2026
c2f459e
chore: Merge branch 'main' into fix/json-schema-spec-support
bilaloumehdi Mar 6, 2026
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38 changes: 4 additions & 34 deletions mcp-core/src/main/java/io/modelcontextprotocol/spec/McpSchema.java
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Original file line number Diff line number Diff line change
Expand Up @@ -1298,27 +1298,6 @@ public ListToolsResult(List<Tool> tools, String nextCursor) {
}
}

/**
* A JSON Schema object that describes the expected structure of arguments or output.
*
* @param type The type of the schema (e.g., "object")
* @param properties The properties of the schema object
* @param required List of required property names
* @param additionalProperties Whether additional properties are allowed
* @param defs Schema definitions using the newer $defs keyword
* @param definitions Schema definitions using the legacy definitions keyword
*/
@JsonInclude(JsonInclude.Include.NON_ABSENT)
@JsonIgnoreProperties(ignoreUnknown = true)
public record JsonSchema( // @formatter:off
@JsonProperty("type") String type,
@JsonProperty("properties") Map<String, Object> properties,
@JsonProperty("required") List<String> required,
@JsonProperty("additionalProperties") Boolean additionalProperties,
@JsonProperty("$defs") Map<String, Object> defs,
@JsonProperty("definitions") Map<String, Object> definitions) { // @formatter:on
}

/**
* Additional properties describing a Tool to clients.
*
Expand Down Expand Up @@ -1363,7 +1342,7 @@ public record Tool( // @formatter:off
@JsonProperty("name") String name,
@JsonProperty("title") String title,
@JsonProperty("description") String description,
@JsonProperty("inputSchema") JsonSchema inputSchema,
@JsonProperty("inputSchema") Map<String, Object> inputSchema,
@JsonProperty("outputSchema") Map<String, Object> outputSchema,
@JsonProperty("annotations") ToolAnnotations annotations,
@JsonProperty("_meta") Map<String, Object> meta) { // @formatter:on
Expand All @@ -1380,7 +1359,7 @@ public static class Builder {

private String description;

private JsonSchema inputSchema;
private Map<String, Object> inputSchema;

private Map<String, Object> outputSchema;

Expand All @@ -1403,13 +1382,13 @@ public Builder description(String description) {
return this;
}

public Builder inputSchema(JsonSchema inputSchema) {
public Builder inputSchema(Map<String, Object> inputSchema) {
this.inputSchema = inputSchema;
return this;
}

public Builder inputSchema(McpJsonMapper jsonMapper, String inputSchema) {
this.inputSchema = parseSchema(jsonMapper, inputSchema);
this.inputSchema = schemaToMap(jsonMapper, inputSchema);
return this;
}

Expand Down Expand Up @@ -1450,15 +1429,6 @@ private static Map<String, Object> schemaToMap(McpJsonMapper jsonMapper, String
}
}

private static JsonSchema parseSchema(McpJsonMapper jsonMapper, String schema) {
try {
return jsonMapper.readValue(schema, JsonSchema.class);
}
catch (IOException e) {
throw new IllegalArgumentException("Invalid schema: " + schema, e);
}
}

/**
* Used by the client to call a tool provided by the server.
*
Expand Down
27 changes: 5 additions & 22 deletions mcp-core/src/test/java/io/modelcontextprotocol/server/AsyncToolSpecificationBuilderTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -25,7 +25,6 @@
import reactor.core.publisher.Mono;
import reactor.test.StepVerifier;

import static io.modelcontextprotocol.util.ToolsUtils.EMPTY_JSON_SCHEMA;
import static org.assertj.core.api.Assertions.assertThat;
import static org.assertj.core.api.Assertions.assertThatCode;
import static org.assertj.core.api.Assertions.assertThatThrownBy;
Expand All @@ -41,11 +40,7 @@ class AsyncToolSpecificationBuilderTest {
@Test
void builderShouldCreateValidAsyncToolSpecification() {

Tool tool = McpSchema.Tool.builder()
.name("test-tool")
.title("A test tool")
.inputSchema(EMPTY_JSON_SCHEMA)
.build();
Tool tool = McpSchema.Tool.builder().name("test-tool").title("A test tool").inputSchema(Map.of()).build();

McpServerFeatures.AsyncToolSpecification specification = McpServerFeatures.AsyncToolSpecification.builder()
.tool(tool)
Expand All @@ -68,11 +63,7 @@ void builderShouldThrowExceptionWhenToolIsNull() {

@Test
void builderShouldThrowExceptionWhenCallToolIsNull() {
Tool tool = McpSchema.Tool.builder()
.name("test-tool")
.title("A test tool")
.inputSchema(EMPTY_JSON_SCHEMA)
.build();
Tool tool = McpSchema.Tool.builder().name("test-tool").title("A test tool").inputSchema(Map.of()).build();

assertThatThrownBy(() -> McpServerFeatures.AsyncToolSpecification.builder().tool(tool).build())
.isInstanceOf(IllegalArgumentException.class)
Expand All @@ -81,11 +72,7 @@ void builderShouldThrowExceptionWhenCallToolIsNull() {

@Test
void builderShouldAllowMethodChaining() {
Tool tool = McpSchema.Tool.builder()
.name("test-tool")
.title("A test tool")
.inputSchema(EMPTY_JSON_SCHEMA)
.build();
Tool tool = McpSchema.Tool.builder().name("test-tool").title("A test tool").inputSchema(Map.of()).build();
McpServerFeatures.AsyncToolSpecification.Builder builder = McpServerFeatures.AsyncToolSpecification.builder();

// Then - verify method chaining returns the same builder instance
Expand All @@ -100,7 +87,7 @@ void builtSpecificationShouldExecuteCallToolCorrectly() {
Tool tool = McpSchema.Tool.builder()
.name("calculator")
.title("Simple calculator")
.inputSchema(EMPTY_JSON_SCHEMA)
.inputSchema(Map.of())
.build();
String expectedResult = "42";

Expand All @@ -124,11 +111,7 @@ void builtSpecificationShouldExecuteCallToolCorrectly() {

@Test
void fromSyncShouldConvertSyncToolSpecificationCorrectly() {
Tool tool = McpSchema.Tool.builder()
.name("sync-tool")
.title("A sync tool")
.inputSchema(EMPTY_JSON_SCHEMA)
.build();
Tool tool = McpSchema.Tool.builder().name("sync-tool").title("A sync tool").inputSchema(Map.of()).build();
String expectedResult = "sync result";

// Create a sync tool specification
Expand Down
13 changes: 4 additions & 9 deletions mcp-core/src/test/java/io/modelcontextprotocol/server/SyncToolSpecificationBuilderTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -22,7 +22,6 @@
import org.junit.jupiter.api.Test;
import org.slf4j.LoggerFactory;

import static io.modelcontextprotocol.util.ToolsUtils.EMPTY_JSON_SCHEMA;
import static org.assertj.core.api.Assertions.assertThat;
import static org.assertj.core.api.Assertions.assertThatCode;
import static org.assertj.core.api.Assertions.assertThatThrownBy;
Expand All @@ -38,7 +37,7 @@ class SyncToolSpecificationBuilderTest {
@Test
void builderShouldCreateValidSyncToolSpecification() {

Tool tool = Tool.builder().name("test-tool").title("A test tool").inputSchema(EMPTY_JSON_SCHEMA).build();
Tool tool = Tool.builder().name("test-tool").title("A test tool").inputSchema(Map.of()).build();

McpServerFeatures.SyncToolSpecification specification = McpServerFeatures.SyncToolSpecification.builder()
.tool(tool)
Expand All @@ -62,7 +61,7 @@ void builderShouldThrowExceptionWhenToolIsNull() {

@Test
void builderShouldThrowExceptionWhenCallToolIsNull() {
Tool tool = Tool.builder().name("test-tool").description("A test tool").inputSchema(EMPTY_JSON_SCHEMA).build();
Tool tool = Tool.builder().name("test-tool").description("A test tool").inputSchema(Map.of()).build();

assertThatThrownBy(() -> McpServerFeatures.SyncToolSpecification.builder().tool(tool).build())
.isInstanceOf(IllegalArgumentException.class)
Expand All @@ -71,7 +70,7 @@ void builderShouldThrowExceptionWhenCallToolIsNull() {

@Test
void builderShouldAllowMethodChaining() {
Tool tool = Tool.builder().name("test-tool").description("A test tool").inputSchema(EMPTY_JSON_SCHEMA).build();
Tool tool = Tool.builder().name("test-tool").description("A test tool").inputSchema(Map.of()).build();
McpServerFeatures.SyncToolSpecification.Builder builder = McpServerFeatures.SyncToolSpecification.builder();

// Then - verify method chaining returns the same builder instance
Expand All @@ -83,11 +82,7 @@ void builderShouldAllowMethodChaining() {

@Test
void builtSpecificationShouldExecuteCallToolCorrectly() {
Tool tool = Tool.builder()
.name("calculator")
.description("Simple calculator")
.inputSchema(EMPTY_JSON_SCHEMA)
.build();
Tool tool = Tool.builder().name("calculator").description("Simple calculator").inputSchema(Map.of()).build();
String expectedResult = "42";

McpServerFeatures.SyncToolSpecification specification = McpServerFeatures.SyncToolSpecification.builder()
Expand Down
3 changes: 0 additions & 3 deletions mcp-core/src/test/java/io/modelcontextprotocol/util/ToolsUtils.java
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Original file line number Diff line number Diff line change
Expand Up @@ -9,7 +9,4 @@ public final class ToolsUtils {
private ToolsUtils() {
}

public static final McpSchema.JsonSchema EMPTY_JSON_SCHEMA = new McpSchema.JsonSchema("object",
Collections.emptyMap(), null, null, null, null);

}
43 changes: 17 additions & 26 deletions mcp-test/src/main/java/io/modelcontextprotocol/AbstractMcpClientServerIntegrationTests.java
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Original file line number Diff line number Diff line change
Expand Up @@ -54,7 +54,6 @@
import org.junit.jupiter.params.provider.ValueSource;
import reactor.core.publisher.Mono;

import static io.modelcontextprotocol.util.ToolsUtils.EMPTY_JSON_SCHEMA;
import static net.javacrumbs.jsonunit.assertj.JsonAssertions.assertThatJson;
import static net.javacrumbs.jsonunit.assertj.JsonAssertions.json;
import static org.assertj.core.api.Assertions.assertThat;
Expand Down Expand Up @@ -106,7 +105,7 @@ void testCreateMessageWithoutSamplingCapabilities(String clientType) {
var clientBuilder = clientBuilders.get(clientType);

McpServerFeatures.AsyncToolSpecification tool = McpServerFeatures.AsyncToolSpecification.builder()
.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(EMPTY_JSON_SCHEMA).build())
.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(Map.of()).build())
.callHandler((exchange, request) -> {
return exchange.createMessage(mock(McpSchema.CreateMessageRequest.class))
.then(Mono.just(mock(CallToolResult.class)));
Expand Down Expand Up @@ -156,7 +155,7 @@ void testCreateMessageSuccess(String clientType) {
AtomicReference<CreateMessageResult> samplingResult = new AtomicReference<>();

McpServerFeatures.AsyncToolSpecification tool = McpServerFeatures.AsyncToolSpecification.builder()
.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(EMPTY_JSON_SCHEMA).build())
.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(Map.of()).build())
.callHandler((exchange, request) -> {

var createMessageRequest = McpSchema.CreateMessageRequest.builder()
Expand Down Expand Up @@ -235,7 +234,7 @@ void testCreateMessageWithRequestTimeoutSuccess(String clientType) throws Interr
AtomicReference<CreateMessageResult> samplingResult = new AtomicReference<>();

McpServerFeatures.AsyncToolSpecification tool = McpServerFeatures.AsyncToolSpecification.builder()
.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(EMPTY_JSON_SCHEMA).build())
.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(Map.of()).build())
.callHandler((exchange, request) -> {

var createMessageRequest = McpSchema.CreateMessageRequest.builder()
Expand Down Expand Up @@ -310,7 +309,7 @@ void testCreateMessageWithRequestTimeoutFail(String clientType) throws Interrupt
.build();

McpServerFeatures.AsyncToolSpecification tool = McpServerFeatures.AsyncToolSpecification.builder()
.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(EMPTY_JSON_SCHEMA).build())
.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(Map.of()).build())
.callHandler((exchange, request) -> {

var createMessageRequest = McpSchema.CreateMessageRequest.builder()
Expand Down Expand Up @@ -360,7 +359,7 @@ void testCreateElicitationWithoutElicitationCapabilities(String clientType) {
var clientBuilder = clientBuilders.get(clientType);

McpServerFeatures.AsyncToolSpecification tool = McpServerFeatures.AsyncToolSpecification.builder()
.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(EMPTY_JSON_SCHEMA).build())
.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(Map.of()).build())
.callHandler((exchange, request) -> exchange.createElicitation(mock(ElicitRequest.class))
.then(Mono.just(mock(CallToolResult.class))))
.build();
Expand Down Expand Up @@ -406,7 +405,7 @@ void testCreateElicitationSuccess(String clientType) {
AtomicReference<McpSchema.ElicitResult> elicitResultRef = new AtomicReference<>();

McpServerFeatures.AsyncToolSpecification tool = McpServerFeatures.AsyncToolSpecification.builder()
.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(EMPTY_JSON_SCHEMA).build())
.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(Map.of()).build())
.callHandler((exchange, request) -> {

var elicitationRequest = McpSchema.ElicitRequest.builder()
Expand Down Expand Up @@ -465,7 +464,7 @@ void testCreateElicitationWithRequestTimeoutSuccess(String clientType) {
AtomicReference<ElicitResult> resultRef = new AtomicReference<>();

McpServerFeatures.AsyncToolSpecification tool = McpServerFeatures.AsyncToolSpecification.builder()
.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(EMPTY_JSON_SCHEMA).build())
.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(Map.of()).build())
.callHandler((exchange, request) -> {

var elicitationRequest = McpSchema.ElicitRequest.builder()
Expand Down Expand Up @@ -536,7 +535,7 @@ void testCreateElicitationWithRequestTimeoutFail(String clientType) {
AtomicReference<ElicitResult> resultRef = new AtomicReference<>();

McpServerFeatures.AsyncToolSpecification tool = McpServerFeatures.AsyncToolSpecification.builder()
.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(EMPTY_JSON_SCHEMA).build())
.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(Map.of()).build())
.callHandler((exchange, request) -> {

var elicitationRequest = ElicitRequest.builder()
Expand Down Expand Up @@ -634,7 +633,7 @@ void testRootsWithoutCapability(String clientType) {
var clientBuilder = clientBuilders.get(clientType);

McpServerFeatures.SyncToolSpecification tool = McpServerFeatures.SyncToolSpecification.builder()
.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(EMPTY_JSON_SCHEMA).build())
.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(Map.of()).build())
.callHandler((exchange, request) -> {

exchange.listRoots(); // try to list roots
Expand Down Expand Up @@ -776,7 +775,7 @@ void testToolCallSuccess(String clientType) {
.addContent(new McpSchema.TextContent("CALL RESPONSE; ctx=importantValue"))
.build();
McpServerFeatures.SyncToolSpecification tool1 = McpServerFeatures.SyncToolSpecification.builder()
.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(EMPTY_JSON_SCHEMA).build())
.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(Map.of()).build())
.callHandler((exchange, request) -> {

try {
Expand Down Expand Up @@ -827,11 +826,7 @@ void testThrowingToolCallIsCaughtBeforeTimeout(String clientType) {
McpSyncServer mcpServer = prepareSyncServerBuilder()
.capabilities(ServerCapabilities.builder().tools(true).build())
.tools(McpServerFeatures.SyncToolSpecification.builder()
.tool(Tool.builder()
.name("tool1")
.description("tool1 description")
.inputSchema(EMPTY_JSON_SCHEMA)
.build())
.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(Map.of()).build())
.callHandler((exchange, request) -> {
// We trigger a timeout on blocking read, raising an exception
Mono.never().block(Duration.ofSeconds(1));
Expand Down Expand Up @@ -869,7 +864,7 @@ void testToolCallSuccessWithTranportContextExtraction(String clientType) {
.addContent(new McpSchema.TextContent("CALL RESPONSE; ctx=value"))
.build();
McpServerFeatures.SyncToolSpecification tool1 = McpServerFeatures.SyncToolSpecification.builder()
.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(EMPTY_JSON_SCHEMA).build())
.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(Map.of()).build())
.callHandler((exchange, request) -> {

McpTransportContext transportContext = exchange.transportContext();
Expand Down Expand Up @@ -925,7 +920,7 @@ void testToolListChangeHandlingSuccess(String clientType) {
.build();

McpServerFeatures.SyncToolSpecification tool1 = McpServerFeatures.SyncToolSpecification.builder()
.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(EMPTY_JSON_SCHEMA).build())
.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(Map.of()).build())
.callHandler((exchange, request) -> {
// perform a blocking call to a remote service
try {
Expand Down Expand Up @@ -991,11 +986,7 @@ void testToolListChangeHandlingSuccess(String clientType) {

// Add a new tool
McpServerFeatures.SyncToolSpecification tool2 = McpServerFeatures.SyncToolSpecification.builder()
.tool(Tool.builder()
.name("tool2")
.description("tool2 description")
.inputSchema(EMPTY_JSON_SCHEMA)
.build())
.tool(Tool.builder().name("tool2").description("tool2 description").inputSchema(Map.of()).build())
.callHandler((exchange, request) -> callResponse)
.build();

Expand Down Expand Up @@ -1046,7 +1037,7 @@ void testLoggingNotification(String clientType) throws InterruptedException {
.tool(Tool.builder()
.name("logging-test")
.description("Test logging notifications")
.inputSchema(EMPTY_JSON_SCHEMA)
.inputSchema(Map.of())
.build())
.callHandler((exchange, request) -> {

Expand Down Expand Up @@ -1163,7 +1154,7 @@ void testProgressNotification(String clientType) throws InterruptedException {
.tool(McpSchema.Tool.builder()
.name("progress-test")
.description("Test progress notifications")
.inputSchema(EMPTY_JSON_SCHEMA)
.inputSchema(Map.of())
.build())
.callHandler((exchange, request) -> {

Expand Down Expand Up @@ -1321,7 +1312,7 @@ void testPingSuccess(String clientType) {
.tool(Tool.builder()
.name("ping-async-test")
.description("Test ping async behavior")
.inputSchema(EMPTY_JSON_SCHEMA)
.inputSchema(Map.of())
.build())
.callHandler((exchange, request) -> {

Expand Down
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