Module: MCP::Methods

Defined in:
lib/mcp/methods.rb

Defined Under Namespace

Classes: MissingRequiredCapabilityError

Constant Summary collapse

INITIALIZE = 
"initialize"
PING = 
"ping"
LOGGING_SET_LEVEL = 
"logging/setLevel"
SERVER_DISCOVER =

Sessionless capability discovery (MCP 2026-07-28 draft, SEP-2575).

"server/discover"
SUBSCRIPTIONS_LISTEN =

Long-lived notification subscription stream (MCP 2026-07-28, SEP-2575), replacing the legacy HTTP GET listening stream. Served at the transport layer (Streamable HTTP modern path); transports without streaming support answer -32601.

"subscriptions/listen"
PROMPTS_GET = 
"prompts/get"
PROMPTS_LIST = 
"prompts/list"
COMPLETION_COMPLETE = 
"completion/complete"
RESOURCES_LIST = 
"resources/list"
RESOURCES_READ = 
"resources/read"
RESOURCES_TEMPLATES_LIST = 
"resources/templates/list"
RESOURCES_SUBSCRIBE = 
"resources/subscribe"
RESOURCES_UNSUBSCRIBE = 
"resources/unsubscribe"
TOOLS_CALL = 
"tools/call"
TOOLS_LIST = 
"tools/list"
MODERN_REMOVED_METHODS =

RPC methods the stateless modern lifecycle removes (MCP 2026-07-28, SEP-2575): initialize is replaced by the per-request _meta envelope plus server/discover, logging/setLevel by the envelope's logLevel member, and ping and the resource subscription pair by the connectionless model, which leaves nothing to keep alive or subscribe on. A modern-era request naming one of these answers with -32601 Method not found (HTTP 404 on Streamable HTTP).

[
  INITIALIZE,
  PING,
  LOGGING_SET_LEVEL,
  RESOURCES_SUBSCRIBE,
  RESOURCES_UNSUBSCRIBE,
].freeze
ROOTS_LIST = 
"roots/list"
SAMPLING_CREATE_MESSAGE = 
"sampling/createMessage"
ELICITATION_CREATE = 
"elicitation/create"
NOTIFICATIONS_INITIALIZED =

Notification methods

"notifications/initialized"
NOTIFICATIONS_TOOLS_LIST_CHANGED = 
"notifications/tools/list_changed"
NOTIFICATIONS_PROMPTS_LIST_CHANGED = 
"notifications/prompts/list_changed"
NOTIFICATIONS_RESOURCES_LIST_CHANGED = 
"notifications/resources/list_changed"
NOTIFICATIONS_RESOURCES_UPDATED = 
"notifications/resources/updated"
NOTIFICATIONS_ROOTS_LIST_CHANGED = 
"notifications/roots/list_changed"
NOTIFICATIONS_MESSAGE = 
"notifications/message"
NOTIFICATIONS_PROGRESS = 
"notifications/progress"
NOTIFICATIONS_CANCELLED = 
"notifications/cancelled"
NOTIFICATIONS_ELICITATION_COMPLETE = 
"notifications/elicitation/complete"
NOTIFICATIONS_SUBSCRIPTIONS_ACKNOWLEDGED =

First message on a subscriptions/listen stream (SEP-2575): reports the subset of requested notification types the server agreed to honor.

"notifications/subscriptions/acknowledged"

Class Method Summary collapse

Class Method Details

.ensure_capability!(method, capabilities) ⇒ Object 



77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
 
# File 'lib/mcp/methods.rb', line 77

def ensure_capability!(method, capabilities)
  case method
  when PROMPTS_GET, PROMPTS_LIST
    require_capability!(method, capabilities, :prompts)
  when NOTIFICATIONS_PROMPTS_LIST_CHANGED
    require_capability!(method, capabilities, :prompts)
    require_capability!(method, capabilities, :prompts, :listChanged)
  when RESOURCES_LIST, RESOURCES_TEMPLATES_LIST, RESOURCES_READ
    require_capability!(method, capabilities, :resources)
  when NOTIFICATIONS_RESOURCES_LIST_CHANGED
    require_capability!(method, capabilities, :resources)
    require_capability!(method, capabilities, :resources, :listChanged)
  when RESOURCES_SUBSCRIBE, RESOURCES_UNSUBSCRIBE, NOTIFICATIONS_RESOURCES_UPDATED
    require_capability!(method, capabilities, :resources)
    require_capability!(method, capabilities, :resources, :subscribe)
  when TOOLS_CALL, TOOLS_LIST
    require_capability!(method, capabilities, :tools)
  when NOTIFICATIONS_TOOLS_LIST_CHANGED
    require_capability!(method, capabilities, :tools)
    require_capability!(method, capabilities, :tools, :listChanged)
  when LOGGING_SET_LEVEL, NOTIFICATIONS_MESSAGE
    require_capability!(method, capabilities, :logging)
  when COMPLETION_COMPLETE
    require_capability!(method, capabilities, :completions)
  when ROOTS_LIST
    require_capability!(method, capabilities, :roots)
  when SAMPLING_CREATE_MESSAGE
    require_capability!(method, capabilities, :sampling)
  when ELICITATION_CREATE
    require_capability!(method, capabilities, :elicitation)
  when INITIALIZE, PING, SERVER_DISCOVER, NOTIFICATIONS_INITIALIZED, NOTIFICATIONS_ROOTS_LIST_CHANGED,
       NOTIFICATIONS_PROGRESS, NOTIFICATIONS_CANCELLED, NOTIFICATIONS_ELICITATION_COMPLETE
    # No specific capability required.
  end
end

.notification?(method) ⇒ Boolean

Returns:

  • (Boolean) 


73
74
75
 
# File 'lib/mcp/methods.rb', line 73

def notification?(method)
  method.is_a?(String) && method.start_with?("notifications/")
end