add client sample (#55)
* add mcp Client example * Add sample links for weather-stdio-server and kotlin-mcp-client to main readme
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Pavel Gorgulov
GitHub
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2 changed files with 697 additions and 0 deletions
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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.*
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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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import io.modelcontextprotocol.kotlin.sdk.Implementation
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import io.modelcontextprotocol.kotlin.sdk.TextContent
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import io.modelcontextprotocol.kotlin.sdk.client.Client
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import io.modelcontextprotocol.kotlin.sdk.client.StdioClientTransport
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import kotlinx.coroutines.runBlocking
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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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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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// 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_3_5_SONNET_20241022)
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.maxTokens(1024)
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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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private fun JsonObject.toJsonValue(): JsonValue {
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val mapper = ObjectMapper()
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val node = mapper.readTree(this.toString())
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return JsonValue.fromJsonNode(node)
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}
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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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}
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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())
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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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} ?: emptyList()
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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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}
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}
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// Process a user query and return a string response
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suspend fun processQuery(query: String): String {
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// Create an initial message with a user's query
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val messages = mutableListOf(
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MessageParam.builder()
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.role(MessageParam.Role.USER)
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.content(query)
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.build()
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)
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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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.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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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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// 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 toolArgs =
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content.toolUse().get()._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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name = toolName,
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arguments = toolArgs ?: emptyMap()
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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": ${result?.content?.joinToString("\n") { (it as TextContent).text ?: "" }}
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""".trimIndent()
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)
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.build()
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)
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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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// Append the updated response to final text
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finalText.add(aiResponse.content().first().text().getOrNull()?.text() ?: "")
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}
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}
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}
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return finalText.joinToString("\n", prefix = "", postfix = "")
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}
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// Main chat loop for interacting with the user
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suspend fun chatLoop() {
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println("\nMCP Client Started!")
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println("Type your queries or 'quit' to exit.")
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while (true) {
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print("\nQuery: ")
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val message = readLine() ?: 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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}
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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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}
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}
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@ -0,0 +1,13 @@
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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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if (args.isEmpty()) throw IllegalArgumentException("Usage: java -jar <your_path>/build/libs/kotlin-mcp-client-0.1.0-all.jar <path_to_server_script>")
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val serverPath = args.first()
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val client = MCPClient()
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client.use {
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client.connectToServer(serverPath)
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client.chatLoop()
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}
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}
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