feat: add roots-demo sample for client roots capability

samples/README.md

@@ -13,6 +13,7 @@ For background on the protocol itself, see the [MCP documentation](https://model
 | [kotlin-mcp-server](./kotlin-mcp-server)               | Server            | STDIO, SSE      | Tools, Resources, Prompts          |
 | [weather-stdio-server](./weather-stdio-server)         | Server            | STDIO           | Tools                              |
 | [kotlin-mcp-client](./kotlin-mcp-client)               | Client            | STDIO           | Tool discovery & invocation        |
+| [roots-demo](./roots-demo)                             | Client + Server   | In-memory       | Roots                              |
 | [notebooks](./notebooks)                               | Client (Notebook) | Streamable HTTP | Tool discovery & invocation        |
 
 ## Getting Started
@@ -56,6 +57,12 @@ An interactive CLI client that connects to any MCP server over STDIO and routes
 Anthropic's Claude API, bridging MCP tools with LLM conversations.
 [Read more →](./kotlin-mcp-client)
 
+### Roots Demo
+
+A minimal in-memory sample demonstrating the MCP Roots capability — how a client exposes
+filesystem roots to a server, and how the server reacts when the root list changes.
+[Read more →](./roots-demo)
+
 ### MCP Client Notebook
 
 A Kotlin notebook that connects to a remote MCP server via Streamable HTTP and demonstrates ping,

samples/roots-demo/README.md

@@ -0,0 +1,54 @@
+# Roots Demo
+
+A minimal sample demonstrating the MCP **Roots** capability using in-memory
+[ChannelTransport](../../kotlin-sdk-testing/src/commonMain/kotlin/io/modelcontextprotocol/kotlin/sdk/testing/ChannelTransport.kt).
+
+## Overview
+
+[Roots](https://modelcontextprotocol.io/docs/concepts/roots) allow an MCP client to
+expose filesystem locations to a server. The server can request the list of roots and
+receive notifications when that list changes.
+
+This sample shows the full roots lifecycle:
+
+1. **Client declares roots capability** — the client advertises `roots` with
+   `listChanged = true` during initialization.
+2. **Client registers roots** — `addRoot(uri, name)` adds roots that the server can
+   discover.
+3. **Server queries roots** — `serverSession.listRoots()` sends a `roots/list`
+   request to the client.
+4. **Client sends change notification** — after dynamically adding or removing roots,
+   the client calls `sendRootsListChanged()` so the server knows to re-fetch.
+5. **Server reacts to changes** — the server listens for
+   `notifications/roots/list_changed` and re-queries the updated root list.
+
+## Prerequisites
+
+- JDK 17+
+
+## Build & Run
+
+```shell
+./gradlew run
+```
+
+The program connects a client and server in-process using `ChannelTransport` and
+prints the roots exchange to the console. No external server or network is required.
+
+## MCP Capabilities
+
+### Client
+
+| Capability | Details |
+|-----------|---------|
+| `roots` | Advertised with `listChanged = true`. Registers project directories and notifies the server on changes. |
+
+### Server
+
+Demonstrates consuming the roots capability by calling `listRoots()` and listening for
+`notifications/roots/list_changed`.
+
+## Additional Resources
+
+- [MCP Roots Specification](https://modelcontextprotocol.io/docs/concepts/roots)
+- [Kotlin MCP SDK](https://github.com/modelcontextprotocol/kotlin-sdk)

samples/roots-demo/build.gradle.kts

@@ -0,0 +1,27 @@
+plugins {
+    alias(libs.plugins.kotlin.jvm)
+    alias(libs.plugins.shadow)
+    application
+}
+
+group = "org.example"
+version = "0.1.0"
+
+application {
+    mainClass.set("io.modelcontextprotocol.sample.roots.MainKt")
+}
+
+dependencies {
+    implementation(libs.mcp.kotlin.client)
+    implementation(libs.mcp.kotlin.server)
+    implementation(libs.mcp.kotlin.testing)
+    implementation(libs.slf4j.simple)
+}
+
+tasks.test {
+    useJUnitPlatform()
+}
+
+kotlin {
+    jvmToolchain(17)
+}

samples/roots-demo/gradle.properties

@@ -0,0 +1,5 @@
+org.gradle.configuration-cache=true
+org.gradle.parallel=true
+org.gradle.caching=true
+
+#mcp.kotlin.overrideVersion=0.0.1-SNAPSHOT

samples/roots-demo/gradle/libs.versions.toml

@@ -0,0 +1,15 @@
+[versions]
+kotlin = "2.3.21"
+mcp-kotlin = "0.12.0"
+shadow = "9.4.1"
+slf4j = "2.0.17"
+
+[libraries]
+mcp-kotlin-client = { group = "io.modelcontextprotocol", name = "kotlin-sdk-client", version.ref = "mcp-kotlin" }
+mcp-kotlin-server = { group = "io.modelcontextprotocol", name = "kotlin-sdk-server", version.ref = "mcp-kotlin" }
+mcp-kotlin-testing = { group = "io.modelcontextprotocol", name = "kotlin-sdk-testing", version.ref = "mcp-kotlin" }
+slf4j-simple = { group = "org.slf4j", name = "slf4j-simple", version.ref = "slf4j" }
+
+[plugins]
+kotlin-jvm = { id = "org.jetbrains.kotlin.jvm", version.ref = "kotlin" }
+shadow = { id = "com.gradleup.shadow", version.ref = "shadow" }

samples/roots-demo/gradle/wrapper/gradle-wrapper.properties

@@ -0,0 +1,9 @@
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-9.5.0-bin.zip
+networkTimeout=10000
+retries=0
+retryBackOffMs=500
+validateDistributionUrl=true
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists