MCP注解支持多种特殊参数类型，这些参数可为被注解的方法提供额外上下文和功能。它们由框架自动注入，且不会被纳入JSON模式生成。
特殊参数类型
McpMeta
McpMeta类用于获取MCP请求、通知和结果中的元数据。
概述
作为方法参数使用时会被自动注入
不计入参数数量限制，且不参与JSON模式生成
通过get(String key)方法可便捷获取元数据
若请求中无元数据，将注入空的McpMeta对象
在工具中的使用
@McpTool(name = "contextual-tool", description = "Tool with metadata access")
public String processWithContext(
@McpToolParam(description = "Input data", required = true) String data,
McpMeta meta) {
// Access metadata from the request
String userId = (String) meta.get("userId");
String sessionId = (String) meta.get("sessionId");
String userRole = (String) meta.get("userRole");
// Use metadata to customize behavior
if ("admin".equals(userRole)) {
return processAsAdmin(data, userId);
} else {
return processAsUser(data, userId);
}
}在资源中的使用
@McpResource(uri = "secure-data://{id}", name = "Secure Data")
public ReadResourceResult getSecureData(String id, McpMeta meta) {
String requestingUser = (String) meta.get("requestingUser");
String accessLevel = (String) meta.get("accessLevel");
// Check access permissions using metadata
if (!"admin".equals(accessLevel)) {
return new ReadResourceResult(List.of(
new TextResourceContents("secure-data://" + id,
"text/plain", "Access denied")
));
}
String data = loadSecureData(id);
return new ReadResourceResult(List.of(
new TextResourceContents("secure-data://" + id,
"text/plain", data)
));
}在提示词中的使用
@McpPrompt(name = "localized-prompt", description = "Localized prompt generation")
public GetPromptResult localizedPrompt(
@McpArg(name = "topic", required = true) String topic,
McpMeta meta) {
String language = (String) meta.get("language");
String region = (String) meta.get("region");
// Generate localized content based on metadata
String message = generateLocalizedMessage(topic, language, region);
return new GetPromptResult("Localized Prompt",
List.of(new PromptMessage(Role.ASSISTANT, new TextContent(message)))
);
}@McpProgressToken
@McpProgressToken注解用于标记接收MCP请求进度令牌的参数。
概述
参数类型必须为String
自动接收请求中的进度令牌值
不纳入生成的JSON模式
若请求中无进度令牌，将注入null
用于追踪耗时较长的操作
在工具中的使用
@McpTool(name = "long-operation", description = "Long-running operation with progress")
public String performLongOperation(
@McpProgressToken String progressToken,
@McpToolParam(description = "Operation name", required = true) String operation,
@McpToolParam(description = "Duration in seconds", required = true) int duration,
McpSyncServerExchange exchange) {
if (progressToken != null) {
// Send initial progress
exchange.progressNotification(new ProgressNotification(
progressToken, 0.0, 1.0, "Starting " + operation));
// Simulate work with progress updates
for (int i = 1; i 在资源中的使用@McpResource(uri = "large-file://{path}", name = "Large File Resource")
public ReadResourceResult getLargeFile(
@McpProgressToken String progressToken,
String path,
McpSyncServerExchange exchange) {
File file = new File(path);
long fileSize = file.length();
if (progressToken != null) {
// Track file reading progress
exchange.progressNotification(new ProgressNotification(
progressToken, 0.0, fileSize, "Reading file"));
}
String content = readFileWithProgress(file, progressToken, exchange);
if (progressToken != null) {
exchange.progressNotification(new ProgressNotification(
progressToken, fileSize, fileSize, "File read complete"));
}
return new ReadResourceResult(List.of(
new TextResourceContents("large-file://" + path, "text/plain", content)
));
}McpSyncRequestContext / McpAsyncRequestContext请求上下文对象提供了对MCP请求信息和服务端操作的统一访问能力。概述为有状态和无状态操作提供统一接口作为参数使用时会被自动注入不参与JSON模式生成支持日志、进度通知、采样、信息获取等高级功能兼容有状态（服务端交换）和无状态（传输上下文）模式McpSyncRequestContext功能public record UserInfo(String name, String email, int age) {}
@McpTool(name = "advanced-tool", description = "Tool with full server capabilities")
public String advancedTool(
McpSyncRequestContext context,
@McpToolParam(description = "Input", required = true) String input) {
// Send logging notification
context.info("Processing: " + input);
// Ping the client
context.ping();
// Send progress updates
context.progress(50); // 50% complete
// Check if elicitation is supported before using it
if (context.elicitEnabled()) {
// Request additional information from user
StructuredElicitResultelicitResult = context.elicit(
e -> e.message("Need additional information"),
UserInfo.class
);
if (elicitResult.action() == ElicitResult.Action.ACCEPT) {
UserInfo userInfo = elicitResult.structuredContent();
// Use the user information
}
}
// Check if sampling is supported before using it
if (context.sampleEnabled()) {
// Request LLM sampling
CreateMessageResult samplingResult = context.sample(
s -> s.message("Process: " + input)
.modelPreferences(pref -> pref.modelHints("gpt-4"))
);
}
return "Processed with advanced features";
}McpAsyncRequestContext功能public record UserInfo(String name, String email, int age) {}
@McpTool(name = "async-advanced-tool", description = "Async tool with server capabilities")
public MonoasyncAdvancedTool(
McpAsyncRequestContext context,
@McpToolParam(description = "Input", required = true) String input) {
return context.info("Async processing: " + input)
.then(context.progress(25))
.then(context.ping())
.flatMap(v -> {
// Perform elicitation if supported
if (context.elicitEnabled()) {
return context.elicitation(UserInfo.class)
.map(userInfo -> "Processing for user: " + userInfo.name());
}
return Mono.just("Processing...");
})
.flatMap(msg -> {
// Perform sampling if supported
if (context.sampleEnabled()) {
return context.sampling("Process: " + input)
.map(result -> "Completed: " + result);
}
return Mono.just("Completed: " + msg);
});
}McpTransportContext用于无状态操作的轻量级上下文。概述提供最小化上下文，不包含完整的服务端交换能力用于无状态实现作为参数使用时会被自动注入不参与JSON模式生成使用示例@McpTool(name = "stateless-tool", description = "Stateless tool with context")
public String statelessTool(
McpTransportContext context,
@McpToolParam(description = "Input", required = true) String input) {
// Limited context access
// Useful for transport-level operations
return "Processed in stateless mode: " + input;
}
@McpResource(uri = "stateless://{id}", name = "Stateless Resource")
public ReadResourceResult statelessResource(
McpTransportContext context,
String id) {
// Access transport context if needed
String data = loadData(id);
return new ReadResourceResult(List.of(
new TextResourceContents("stateless://" + id, "text/plain", data)
));
}CallToolRequest适用于需要访问完整动态模式请求的工具的特殊参数。概述可访问完整的工具请求支持运行时动态模式处理自动注入且不参与模式生成适用于适配不同输入模式的灵活工具使用示例@McpTool(name = "dynamic-tool", description = "Tool with dynamic schema support")
public CallToolResult processDynamicSchema(CallToolRequest request) {
Mapargs = request.arguments();
// Process based on whatever schema was provided at runtime
StringBuilder result = new StringBuilder("Processed:\n");
for (Map.Entryentry : args.entrySet()) {
result.append(" ").append(entry.getKey())
.append(": ").append(entry.getValue()).append("\n");
}
return CallToolResult.builder()
.addTextContent(result.toString())
.build();
}混合参数@McpTool(name = "hybrid-tool", description = "Tool with typed and dynamic parameters")
public String processHybrid(
@McpToolParam(description = "Operation", required = true) String operation,
@McpToolParam(description = "Priority", required = false) Integer priority,
CallToolRequest request) {
// Use typed parameters for known fields
String result = "Operation: " + operation;
if (priority != null) {
result += " (Priority: " + priority + ")";
}
// Access additional dynamic arguments
MapallArgs = request.arguments();
// Remove known parameters to get only additional ones
MapadditionalArgs = new HashMap<>(allArgs);
additionalArgs.remove("operation");
additionalArgs.remove("priority");
if (!additionalArgs.isEmpty()) {
result += " with " + additionalArgs.size() + " additional parameters";
}
return result;
}携带进度令牌@McpTool(name = "flexible-with-progress", description = "Flexible tool with progress")
public CallToolResult flexibleWithProgress(
@McpProgressToken String progressToken,
CallToolRequest request,
McpSyncServerExchange exchange) {
Mapargs = request.arguments();
if (progressToken != null) {
exchange.progressNotification(new ProgressNotification(
progressToken, 0.0, 1.0, "Processing dynamic request"));
}
// Process dynamic arguments
String result = processDynamicArgs(args);
if (progressToken != null) {
exchange.progressNotification(new ProgressNotification(
progressToken, 1.0, 1.0, "Complete"));
}
return CallToolResult.builder()
.addTextContent(result)
.build();
}参数注入规则自动注入以下参数由框架自动注入：McpMeta - 请求中的元数据@McpProgressToken String - 可用的进度令牌McpSyncServerExchange / McpAsyncServerExchange - 服务端交换上下文McpTransportContext - 无状态操作的传输上下文CallToolRequest - 动态模式的完整工具请求模式生成特殊参数不会被纳入JSON模式生成：不会出现在工具的输入模式中不计入参数数量限制对MCP客户端不可见空值处理McpMeta - 永不为null，无元数据时为空对象@McpProgressToken - 无令牌时可为null服务端交换 - 正确配置时永不为nullCallToolRequest - 工具方法中永不为null最佳实践使用McpMeta获取上下文@McpTool(name = "context-aware", description = "Context-aware tool")
public String contextAware(
@McpToolParam(description = "Data", required = true) String data,
McpMeta meta) {
// Always check for null values in metadata
String userId = (String) meta.get("userId");
if (userId == null) {
userId = "anonymous";
}
return processForUser(data, userId);
}进度令牌空值检查@McpTool(name = "safe-progress", description = "Safe progress handling")
public String safeProgress(
@McpProgressToken String progressToken,
@McpToolParam(description = "Task", required = true) String task,
McpSyncServerExchange exchange) {
// Always check if progress token is available
if (progressToken != null) {
exchange.progressNotification(new ProgressNotification(
progressToken, 0.0, 1.0, "Starting"));
}
// Perform work...
if (progressToken != null) {
exchange.progressNotification(new ProgressNotification(
progressToken, 1.0, 1.0, "Complete"));
}
return "Task completed";
}选择合适的上下文使用McpSyncRequestContext / McpAsyncRequestContext统一访问请求上下文，支持有状态和无状态操作，附带便捷的辅助方法仅需传输级上下文时，使用McpTransportContext处理简单无状态操作最简单的场景可完全省略上下文参数功能可用性检查使用客户端功能前务必检查支持性：@McpTool(name = "capability-aware", description = "Tool that checks capabilities")
public String capabilityAware(
McpSyncRequestContext context,
@McpToolParam(description = "Data", required = true) String data) {
// Check if elicitation is supported before using it
if (context.elicitEnabled()) {
// Safe to use elicitation
var result = context.elicit(UserInfo.class);
// Process result...
}
// Check if sampling is supported before using it
if (context.sampleEnabled()) {
// Safe to use sampling
var samplingResult = context.sample("Process: " + data);
// Process result...
}
// Note: Stateless servers do not support bidirectional operations
// (roots, elicitation, sampling) and will return false for these checks
return "Processed with capability awareness";
} 