docs: update client and server samples (#598)
Updated the client and server examples for further use in the following guides: https://modelcontextprotocol.io/docs/develop/build-server and https://modelcontextprotocol.io/docs/develop/build-client ## How Has This Been Tested? claude desktop, cli ## Breaking Changes NaN ## Types of changes - [ ] Bug fix (non-breaking change which fixes an issue) - [ ] New feature (non-breaking change which adds functionality) - [ ] Breaking change (fix or feature that would cause existing functionality to change) - [x] Example, Documentation update ## Checklist - [x] I have read the [MCP Documentation](https://modelcontextprotocol.io) - [x] My code follows the repository's style guidelines - [x] New and existing tests pass locally - [ ] I have added appropriate error handling - [ ] I have added or updated documentation as needed
This commit is contained in:
Pavel Gorgulov
GitHub
parent
4ecd95218a
commit
921b1fd30e
2 changed files with 311 additions and 228 deletions
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@ -2,10 +2,11 @@ package io.modelcontextprotocol.sample.client
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import com.anthropic.client.okhttp.AnthropicOkHttpClient
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import com.anthropic.core.JsonValue
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import com.anthropic.models.messages.ContentBlockParam
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import com.anthropic.models.messages.MessageCreateParams
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import com.anthropic.models.messages.MessageParam
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import com.anthropic.models.messages.Model
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import com.anthropic.models.messages.Tool
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import com.anthropic.models.messages.ToolResultBlockParam
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import com.anthropic.models.messages.ToolUnion
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import com.fasterxml.jackson.core.type.TypeReference
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import com.fasterxml.jackson.databind.ObjectMapper
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@ -14,24 +15,28 @@ import io.modelcontextprotocol.kotlin.sdk.client.StdioClientTransport
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import io.modelcontextprotocol.kotlin.sdk.types.EmptyJsonObject
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import io.modelcontextprotocol.kotlin.sdk.types.Implementation
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import io.modelcontextprotocol.kotlin.sdk.types.TextContent
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import kotlinx.coroutines.Dispatchers
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import kotlinx.coroutines.runBlocking
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import kotlinx.coroutines.yield
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import kotlinx.coroutines.withContext
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import kotlinx.io.asSink
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import kotlinx.io.asSource
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import kotlinx.io.buffered
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import kotlinx.serialization.json.JsonObject
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import kotlin.jvm.optionals.getOrNull
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import java.util.concurrent.TimeUnit
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class MCPClient : AutoCloseable {
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// Configures using the `ANTHROPIC_API_KEY` and `ANTHROPIC_AUTH_TOKEN` environment variables
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private val anthropic = AnthropicOkHttpClient.fromEnv()
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private const val MODEL = "claude-sonnet-4-20250514"
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private const val MAX_TOKENS = 1024L
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class MCPClient(apiKey: String) : AutoCloseable {
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private val anthropic = AnthropicOkHttpClient.builder()
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.apiKey(apiKey)
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.build()
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// Initialize MCP client
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private val mcp: Client = Client(clientInfo = Implementation(name = "mcp-client-cli", version = "1.0.0"))
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private val messageParamsBuilder: MessageCreateParams.Builder = MessageCreateParams.builder()
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.model(Model.CLAUDE_4_SONNET_20250514)
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.maxTokens(1024)
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// Server process reference for cleanup
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private var serverProcess: Process? = null
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// List of tools offered by the server
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private lateinit var tools: List<ToolUnion>
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@ -44,52 +49,52 @@ class MCPClient : AutoCloseable {
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// Connect to the server using the path to the server
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suspend fun connectToServer(serverScriptPath: String) {
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try {
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// Build the command based on the file extension of the server script
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val command = buildList {
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when (serverScriptPath.substringAfterLast(".")) {
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"js" -> add("node")
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"py" -> add(if (System.getProperty("os.name").lowercase().contains("win")) "python" else "python3")
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"jar" -> addAll(listOf("java", "-jar"))
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else -> throw IllegalArgumentException("Server script must be a .js, .py or .jar file")
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}
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add(serverScriptPath)
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// Build the command based on the file extension of the server script
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val command = buildList {
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when (serverScriptPath.substringAfterLast(".")) {
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"js" -> add("node")
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"py" -> add(if (System.getProperty("os.name").lowercase().contains("win")) "python" else "python3")
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"jar" -> addAll(listOf("java", "-jar"))
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else -> throw IllegalArgumentException("Server script must be a .js, .py or .jar file")
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}
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// Start the server process
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val process = ProcessBuilder(command).start()
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// Setup I/O transport using the process streams
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val transport = StdioClientTransport(
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input = process.inputStream.asSource().buffered(),
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output = process.outputStream.asSink().buffered(),
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)
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// Connect the MCP client to the server using the transport
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mcp.connect(transport)
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// Request the list of available tools from the server
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val toolsResult = mcp.listTools()
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tools = toolsResult.tools.map { tool ->
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ToolUnion.ofTool(
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Tool.builder()
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.name(tool.name)
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.description(tool.description ?: "")
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.inputSchema(
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Tool.InputSchema.builder()
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.type(JsonValue.from(tool.inputSchema.type))
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.properties(tool.inputSchema.properties?.toJsonValue() ?: EmptyJsonObject.toJsonValue())
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.putAdditionalProperty("required", JsonValue.from(tool.inputSchema.required))
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.build(),
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)
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.build(),
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)
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}
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println("Connected to server with tools: ${tools.joinToString(", ") { it.tool().get().name() }}")
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} catch (e: Exception) {
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println("Failed to connect to MCP server: $e")
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throw e
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add(serverScriptPath)
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}
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// Start the server process
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val process = withContext(Dispatchers.IO) {
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ProcessBuilder(command)
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.redirectError(ProcessBuilder.Redirect.INHERIT)
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.start()
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}
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serverProcess = process
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// Setup I/O transport using the process streams
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val transport = StdioClientTransport(
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input = process.inputStream.asSource().buffered(),
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output = process.outputStream.asSink().buffered(),
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)
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// Connect the MCP client to the server using the transport
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mcp.connect(transport)
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// Request the list of available tools from the server
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val toolsResult = mcp.listTools()
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tools = toolsResult.tools.map { tool ->
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ToolUnion.ofTool(
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Tool.builder()
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.name(tool.name)
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.description(tool.description ?: "")
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.inputSchema(
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Tool.InputSchema.builder()
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.type(JsonValue.from(tool.inputSchema.type))
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.properties(tool.inputSchema.properties?.toJsonValue() ?: EmptyJsonObject.toJsonValue())
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.putAdditionalProperty("required", JsonValue.from(tool.inputSchema.required))
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.build(),
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)
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.build(),
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)
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}
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println("Connected to server with tools: ${tools.joinToString(", ") { it.tool().get().name() }}")
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}
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// Process a user query and return a string response
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@ -104,23 +109,29 @@ class MCPClient : AutoCloseable {
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// Send the query to the Anthropic model and get the response
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val response = anthropic.messages().create(
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messageParamsBuilder
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MessageCreateParams.builder()
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.model(MODEL)
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.maxTokens(MAX_TOKENS)
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.messages(messages)
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.tools(tools)
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.build(),
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)
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val finalText = mutableListOf<String>()
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val toolResults = mutableListOf<ContentBlockParam>()
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response.content().forEach { content ->
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when {
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// Append text outputs from the response
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content.isText() -> finalText.add(content.text().getOrNull()?.text() ?: "")
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content.isText() -> finalText.add(content.text().get().text())
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// If the response indicates a tool use, process it further
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content.isToolUse() -> {
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val toolName = content.toolUse().get().name()
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val toolUse = content.toolUse().get()
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val toolName = toolUse.name()
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val toolUseId = toolUse.id()
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val toolArgs =
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content.toolUse().get()._input().convert(object : TypeReference<Map<String, JsonValue>>() {})
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toolUse._input().convert(object : TypeReference<Map<String, JsonValue>>() {})
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// Call the tool with provided arguments
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val result = mcp.callTool(
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@ -129,37 +140,55 @@ class MCPClient : AutoCloseable {
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)
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finalText.add("[Calling tool $toolName with args $toolArgs]")
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// Add the tool result message to the conversation
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messages.add(
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MessageParam.builder()
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.role(MessageParam.Role.USER)
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.content(
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"""
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"type": "tool_result",
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"tool_name": $toolName,
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"result": ${
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result.content.joinToString("\n") {
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(it as TextContent).text
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}
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}
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""".trimIndent(),
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)
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.build(),
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)
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// Build tool_result content block with tool_use_id
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val toolResultContent = result.content
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.filterIsInstance<TextContent>()
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.joinToString("\n") { it.text }
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// Retrieve an updated response after tool execution
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val aiResponse = anthropic.messages().create(
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messageParamsBuilder
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.messages(messages)
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.build(),
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)
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val toolResultBlock = ToolResultBlockParam.builder()
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.toolUseId(toolUseId)
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.content(toolResultContent)
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.apply { if (result.isError == true) isError(true) }
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.build()
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// Append the updated response to final text
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finalText.add(aiResponse.content().first().text().getOrNull()?.text() ?: "")
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toolResults.add(ContentBlockParam.ofToolResult(toolResultBlock))
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}
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}
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}
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// If there were tool calls, send tool results back and get final response
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if (toolResults.isNotEmpty()) {
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// Add the full assistant response (includes tool_use blocks)
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messages.add(
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MessageParam.builder()
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.role(MessageParam.Role.ASSISTANT)
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.contentOfBlockParams(response.content().map { it.toParam() })
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.build(),
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)
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// Add user message with tool results
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messages.add(
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MessageParam.builder()
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.role(MessageParam.Role.USER)
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.contentOfBlockParams(toolResults)
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.build(),
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)
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// Retrieve an updated response after tool execution (without tools)
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val aiResponse = anthropic.messages().create(
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MessageCreateParams.builder()
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.model(MODEL)
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.maxTokens(MAX_TOKENS)
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.messages(messages)
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.build(),
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)
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// Append the updated response to final text
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aiResponse.content()
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.filter { it.isText() }
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.forEach { finalText.add(it.text().get().text()) }
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}
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return finalText.joinToString("\n", prefix = "", postfix = "")
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}
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@ -171,17 +200,27 @@ class MCPClient : AutoCloseable {
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while (true) {
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print("\nQuery: ")
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val message = readlnOrNull() ?: break
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if (message.lowercase() == "quit") break
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val response = processQuery(message)
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println("\n$response")
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yield()
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if (message.trim().lowercase() == "quit") break
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try {
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val response = processQuery(message)
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println("\n$response")
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} catch (e: Exception) {
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println("\nError: ${e.message}")
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}
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}
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}
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override fun close() {
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runBlocking {
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mcp.close()
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anthropic.close()
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}
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serverProcess?.let { process ->
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process.destroy()
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if (!process.waitFor(5, TimeUnit.SECONDS)) {
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process.destroyForcibly()
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}
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}
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anthropic.close()
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}
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}
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@ -3,13 +3,14 @@ package io.modelcontextprotocol.sample.client
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import kotlinx.coroutines.runBlocking
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fun main(args: Array<String>) = runBlocking {
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require(args.isNotEmpty()) {
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"Usage: java -jar <your_path>/build/libs/kotlin-mcp-client-0.1.0-all.jar <path_to_server_script>"
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}
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val serverPath = args.first()
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val client = MCPClient()
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require(args.isNotEmpty()) { "Usage: java -jar <path> <path_to_server_script>" }
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val apiKey = System.getenv("ANTHROPIC_API_KEY")
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require(!apiKey.isNullOrBlank()) { "ANTHROPIC_API_KEY environment variable is not set" }
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val client = MCPClient(apiKey)
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client.use {
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client.connectToServer(serverPath)
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client.connectToServer(args.first())
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client.chatLoop()
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}
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}
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