From dd458b1fb75eee17a50f5b25dde29449cabf96fb Mon Sep 17 00:00:00 2001
From: Koichi ITO <koic.ito@gmail.com>
Date: Mon, 10 Nov 2025 16:24:15 +0900
Subject: [PATCH] Add Elicitation skeleton

The MCP 2025-06-18 specification includes a feature called Elicitation:
https://modelcontextprotocol.io/specification/2025-06-18/client/elicitation

Like Log Level, an implementation is expected to be provided in the near future.
This PR adds Elicitation as a skeleton implementation for now.
---
 README.md                | 3 ++-
 lib/mcp/methods.rb       | 3 +++
 lib/mcp/server.rb        | 1 +
 test/mcp/methods_test.rb | 2 ++
 4 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/README.md b/README.md
index 6fa651db..5d629767 100644
--- a/README.md
+++ b/README.md
@@ -151,11 +151,12 @@ Set `stateless: true` in `MCP::Server::Transports::StreamableHTTPTransport.new`
 transport = MCP::Server::Transports::StreamableHTTPTransport.new(server, stateless: true)
 ```
 
-### Unsupported Features ( to be implemented in future versions )
+### Unsupported Features (to be implemented in future versions)
 
 - Log Level
 - Resource subscriptions
 - Completions
+- Elicitation
 
 ### Usage
 
diff --git a/lib/mcp/methods.rb b/lib/mcp/methods.rb
index f30eaf2e..bf2982ff 100644
--- a/lib/mcp/methods.rb
+++ b/lib/mcp/methods.rb
@@ -21,6 +21,7 @@ module Methods
 
     ROOTS_LIST = "roots/list"
     SAMPLING_CREATE_MESSAGE = "sampling/createMessage"
+    ELICITATION_CREATE = "elicitation/create"
 
     # Notification methods
     NOTIFICATIONS_INITIALIZED = "notifications/initialized"
@@ -76,6 +77,8 @@ def ensure_capability!(method, capabilities)
           require_capability!(method, capabilities, :roots, :listChanged)
         when SAMPLING_CREATE_MESSAGE
           require_capability!(method, capabilities, :sampling)
+        when ELICITATION_CREATE
+          require_capability!(method, capabilities, :elicitation)
         when INITIALIZE, PING, NOTIFICATIONS_INITIALIZED, NOTIFICATIONS_PROGRESS, NOTIFICATIONS_CANCELLED
           # No specific capability required for initialize, ping, progress or cancelled
         end
diff --git a/lib/mcp/server.rb b/lib/mcp/server.rb
index 3a2dd9fe..26896a0a 100644
--- a/lib/mcp/server.rb
+++ b/lib/mcp/server.rb
@@ -80,6 +80,7 @@ def initialize(
         Methods::RESOURCES_UNSUBSCRIBE => ->(_) {},
         Methods::COMPLETION_COMPLETE => ->(_) {},
         Methods::LOGGING_SET_LEVEL => ->(_) {},
+        Methods::ELICITATION_CREATE => ->(_) {},
       }
       @transport = transport
     end
diff --git a/test/mcp/methods_test.rb b/test/mcp/methods_test.rb
index 2022a2a7..0f765d97 100644
--- a/test/mcp/methods_test.rb
+++ b/test/mcp/methods_test.rb
@@ -74,6 +74,8 @@ def ensure_capability_does_not_raise_for(method, capabilities: {})
 
     ensure_capability_raises_error_for Methods::SAMPLING_CREATE_MESSAGE, required_capability_name: "sampling"
 
+    ensure_capability_raises_error_for Methods::ELICITATION_CREATE, required_capability_name: "elicitation"
+
     # Methods and notifications of both server and client
     ensure_capability_does_not_raise_for Methods::PING
     ensure_capability_does_not_raise_for Methods::NOTIFICATIONS_PROGRESS