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Merged
merged 5 commits into from
Jul 13, 2025
Merged

Check all methods & capabilities #63

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e4c9644
Refactor ensure capability tests
kfischer-okarin Jun 14, 2025
127f12f
Add missing method constants
kfischer-okarin Jun 15, 2025
9a00406
Rewrite extend self to class << self
kfischer-okarin Jun 15, 2025
280e835
Refactor capability check
kfischer-okarin Jun 15, 2025
ff92a3d
Add missing checks
kfischer-okarin Jun 15, 2025
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83 changes: 50 additions & 33 deletions lib/mcp/methods.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -19,12 +19,19 @@ module Methods
TOOLS_CALL = "tools/call"
TOOLS_LIST = "tools/list"

ROOTS_LIST = "roots/list"
SAMPLING_CREATE_MESSAGE = "sampling/createMessage"

# Notification methods
NOTIFICATIONS_INITIALIZED = "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"

class MissingRequiredCapabilityError < StandardError
attr_reader :method
Expand All @@ -37,41 +44,51 @@ def initialize(method, capability)
end
end

extend self

def ensure_capability!(method, capabilities)
case method
when PROMPTS_GET, PROMPTS_LIST
unless capabilities[:prompts]
raise MissingRequiredCapabilityError.new(method, :prompts)
end
when RESOURCES_LIST, RESOURCES_TEMPLATES_LIST, RESOURCES_READ, RESOURCES_SUBSCRIBE, RESOURCES_UNSUBSCRIBE
unless capabilities[:resources]
raise MissingRequiredCapabilityError.new(method, :resources)
class << self
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 NOTIFICATIONS_ROOTS_LIST_CHANGED
require_capability!(method, capabilities, :roots)
require_capability!(method, capabilities, :roots, :listChanged)
when SAMPLING_CREATE_MESSAGE
require_capability!(method, capabilities, :sampling)
when INITIALIZE, PING, NOTIFICATIONS_INITIALIZED, NOTIFICATIONS_PROGRESS, NOTIFICATIONS_CANCELLED
# No specific capability required for initialize, ping, progress or cancelled
end
end

if method == RESOURCES_SUBSCRIBE && !capabilities[:resources][:subscribe]
raise MissingRequiredCapabilityError.new(method, :resources_subscribe)
end
when TOOLS_CALL, TOOLS_LIST
unless capabilities[:tools]
raise MissingRequiredCapabilityError.new(method, :tools)
end
when SAMPLING_CREATE_MESSAGE
unless capabilities[:sampling]
raise MissingRequiredCapabilityError.new(method, :sampling)
end
when COMPLETION_COMPLETE
unless capabilities[:completions]
raise MissingRequiredCapabilityError.new(method, :completions)
end
when LOGGING_SET_LEVEL
# Logging is unsupported by the Server
unless capabilities[:logging]
raise MissingRequiredCapabilityError.new(method, :logging)
end
when INITIALIZE, PING
# No specific capability required for initialize or ping
private

def require_capability!(method, capabilities, *keys)
name = keys.join(".") # :resources, :subscribe -> "resources.subscribe"
has_capability = capabilities.dig(*keys)
return if has_capability

raise MissingRequiredCapabilityError.new(method, name)
end
end
end
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118 changes: 63 additions & 55 deletions test/mcp/methods_test.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -5,71 +5,79 @@

module MCP
class MethodsTest < ActiveSupport::TestCase
test "ensure_capability! for tools/list method raises an error if tools capability is not present" do
error = assert_raises(Methods::MissingRequiredCapabilityError) do
Methods.ensure_capability!(Methods::TOOLS_LIST, {})
class << self
def ensure_capability_raises_error_for(method, required_capability_name:, capabilities: {})
test("ensure_capability! for #{method} raises an error if #{required_capability_name} capability is not present") do
error = assert_raises(Methods::MissingRequiredCapabilityError) do
Methods.ensure_capability!(method, capabilities)
end
assert_equal("Server does not support #{required_capability_name} (required for #{method})", error.message)
end
end
assert_equal "Server does not support tools (required for tools/list)", error.message
end

test "ensure_capability! for sampling/createMessage raises an error if sampling capability is not present" do
error = assert_raises(Methods::MissingRequiredCapabilityError) do
Methods.ensure_capability!(Methods::SAMPLING_CREATE_MESSAGE, {})
def ensure_capability_does_not_raise_for(method, capabilities: {})
test("ensure_capability! does not raise for #{method}") do
assert_nothing_raised { Methods.ensure_capability!(method, capabilities) }
end
end
assert_equal "Server does not support sampling (required for sampling/createMessage)", error.message
end

test "ensure_capability! for completion/complete raises an error if completions capability is not present" do
error = assert_raises(Methods::MissingRequiredCapabilityError) do
Methods.ensure_capability!(Methods::COMPLETION_COMPLETE, {})
end
assert_equal "Server does not support completions (required for completion/complete)", error.message
end
# Server methods and notifications
ensure_capability_does_not_raise_for Methods::INITIALIZE

test "ensure_capability! for logging/setLevel raises an error if logging capability is not present" do
error = assert_raises(Methods::MissingRequiredCapabilityError) do
Methods.ensure_capability!(Methods::LOGGING_SET_LEVEL, {})
end
assert_equal "Server does not support logging (required for logging/setLevel)", error.message
end
ensure_capability_raises_error_for Methods::PROMPTS_LIST, required_capability_name: "prompts"
ensure_capability_raises_error_for Methods::PROMPTS_GET, required_capability_name: "prompts"
ensure_capability_raises_error_for Methods::NOTIFICATIONS_PROMPTS_LIST_CHANGED, required_capability_name: "prompts"
ensure_capability_raises_error_for Methods::NOTIFICATIONS_PROMPTS_LIST_CHANGED,
required_capability_name: "prompts.listChanged",
capabilities: { prompts: {} }

test "ensure_capability! for prompts/get and prompts/list raise an error if prompts capability is not present" do
[Methods::PROMPTS_GET, Methods::PROMPTS_LIST].each do |method|
error = assert_raises(Methods::MissingRequiredCapabilityError) do
Methods.ensure_capability!(method, {})
end
assert_equal "Server does not support prompts (required for #{method})", error.message
end
end
ensure_capability_raises_error_for Methods::RESOURCES_LIST, required_capability_name: "resources"
ensure_capability_raises_error_for Methods::RESOURCES_READ, required_capability_name: "resources"
ensure_capability_raises_error_for Methods::RESOURCES_TEMPLATES_LIST, required_capability_name: "resources"
ensure_capability_raises_error_for Methods::NOTIFICATIONS_RESOURCES_LIST_CHANGED, required_capability_name: "resources"
ensure_capability_raises_error_for Methods::NOTIFICATIONS_RESOURCES_LIST_CHANGED,
required_capability_name: "resources.listChanged",
capabilities: { resources: {} }
ensure_capability_raises_error_for Methods::RESOURCES_SUBSCRIBE, required_capability_name: "resources"
ensure_capability_raises_error_for Methods::RESOURCES_SUBSCRIBE,
required_capability_name: "resources.subscribe",
capabilities: { resources: {} }
ensure_capability_raises_error_for Methods::RESOURCES_UNSUBSCRIBE, required_capability_name: "resources"
ensure_capability_raises_error_for Methods::RESOURCES_UNSUBSCRIBE,
required_capability_name: "resources.subscribe",
capabilities: { resources: {} }
ensure_capability_raises_error_for Methods::NOTIFICATIONS_RESOURCES_UPDATED, required_capability_name: "resources"
ensure_capability_raises_error_for Methods::NOTIFICATIONS_RESOURCES_UPDATED,
required_capability_name: "resources.subscribe",
capabilities: { resources: {} }

test "ensure_capability! for resources/list, resources/templates/list, resources/read raise an error if resources capability is not present" do
[Methods::RESOURCES_LIST, Methods::RESOURCES_TEMPLATES_LIST, Methods::RESOURCES_READ].each do |method|
error = assert_raises(Methods::MissingRequiredCapabilityError) do
Methods.ensure_capability!(method, {})
end
assert_equal "Server does not support resources (required for #{method})", error.message
end
end
ensure_capability_raises_error_for Methods::TOOLS_LIST, required_capability_name: "tools"
ensure_capability_raises_error_for Methods::TOOLS_CALL, required_capability_name: "tools"
ensure_capability_raises_error_for Methods::NOTIFICATIONS_TOOLS_LIST_CHANGED, required_capability_name: "tools"
ensure_capability_raises_error_for Methods::NOTIFICATIONS_TOOLS_LIST_CHANGED,
required_capability_name: "tools.listChanged",
capabilities: { tools: {} }

test "ensure_capability! for tools/call and tools/list raise an error if tools capability is not present" do
[Methods::TOOLS_CALL, Methods::TOOLS_LIST].each do |method|
error = assert_raises(Methods::MissingRequiredCapabilityError) do
Methods.ensure_capability!(method, {})
end
assert_equal "Server does not support tools (required for #{method})", error.message
end
end
ensure_capability_raises_error_for Methods::LOGGING_SET_LEVEL, required_capability_name: "logging"
ensure_capability_raises_error_for Methods::NOTIFICATIONS_MESSAGE, required_capability_name: "logging"

test "ensure_capability! for resources/subscribe raises an error if resources subscribe capability is not present" do
error = assert_raises(Methods::MissingRequiredCapabilityError) do
Methods.ensure_capability!(Methods::RESOURCES_SUBSCRIBE, { resources: {} })
end
assert_equal "Server does not support resources_subscribe (required for resources/subscribe)", error.message
end
ensure_capability_raises_error_for Methods::COMPLETION_COMPLETE, required_capability_name: "completions"

test "ensure_capability! does not raise for ping and initialize methods" do
assert_nothing_raised { Methods.ensure_capability!(Methods::PING, {}) }
assert_nothing_raised { Methods.ensure_capability!(Methods::INITIALIZE, {}) }
end
# Client methods and notifications
ensure_capability_does_not_raise_for Methods::NOTIFICATIONS_INITIALIZED

ensure_capability_raises_error_for Methods::ROOTS_LIST, required_capability_name: "roots"
ensure_capability_raises_error_for Methods::NOTIFICATIONS_ROOTS_LIST_CHANGED, required_capability_name: "roots"
ensure_capability_raises_error_for Methods::NOTIFICATIONS_ROOTS_LIST_CHANGED,
required_capability_name: "roots.listChanged",
capabilities: { roots: {} }

ensure_capability_raises_error_for Methods::SAMPLING_CREATE_MESSAGE, required_capability_name: "sampling"

# 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
ensure_capability_does_not_raise_for Methods::NOTIFICATIONS_CANCELLED
end
end
2 changes: 1 addition & 1 deletion test/mcp/server_test.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -635,7 +635,7 @@ def call(message:, server_context: nil)
test "#handle method with missing required nested capability returns an error" do
@server.capabilities = { resources: {} }
response = @server.handle({ jsonrpc: "2.0", method: "resources/subscribe", id: 1 })
assert_equal "Server does not support resources_subscribe (required for resources/subscribe)",
assert_equal "Server does not support resources.subscribe (required for resources/subscribe)",
response[:error][:data]
end

Expand Down