Class: ActionMCP::Tool

Inherits:
Capability show all
Extended by:
SchemaHelpers
Includes:
Callbacks, CurrentHelpers
Defined in:
lib/action_mcp/tool.rb

Overview

Base class for defining tools.

Provides a DSL for specifying metadata, properties, and nested collection schemas. Tools are registered automatically in the ToolsRegistry unless marked as abstract.

Direct Known Subclasses

ApplicationMCPTool

Instance Attribute Summary collapse

Attributes inherited from Capability

#execution_context

Class Method Summary collapse

Instance Method Summary collapse

Methods inherited from Capability

abstract!, abstract?, capability_name, description, #session, #with_context

Constructor Details

#initialize(attributes = {}) ⇒ Tool

Override initialize to validate parameters before ActiveModel conversion



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# File 'lib/action_mcp/tool.rb', line 415

def initialize(attributes = {})
  # Separate additional properties from defined attributes if enabled
  if self.class.accepts_additional_properties?
    defined_keys = self.class.schema_property_keys
    # Use partition for single-pass separation - more efficient than except/slice
    defined_attrs, additional_attrs = attributes.partition { |k, _|
      defined_keys.include?(k.to_s)
    }.map(&:to_h)
    @_additional_params = additional_attrs
    attributes = defined_attrs
  else
    @_additional_params = {}
  end

  # Validate parameters before ActiveModel processes them
  validate_parameter_types(attributes)
  super
end

Instance Attribute Details

#_required_properties ⇒ Array<String>

Returns The required properties of the tool.

Returns:

  • (Array<String>) —

    The required properties of the tool.



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# File 'lib/action_mcp/tool.rb', line 24

class_attribute :_schema_properties, instance_accessor: false, default: {}

#_schema_properties ⇒ Hash

Returns The schema properties of the tool.

Returns:

  • (Hash) —

    The schema properties of the tool.



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# File 'lib/action_mcp/tool.rb', line 24

class_attribute :_schema_properties, instance_accessor: false, default: {}

Class Method Details

.accepts_additional_properties? ⇒ Boolean

Returns whether this tool accepts additional properties

Returns:

  • (Boolean) 


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# File 'lib/action_mcp/tool.rb', line 266

def accepts_additional_properties?
  !_additional_properties.nil? && _additional_properties != false
end

.additional_properties(enabled = nil) ⇒ Object

Sets or retrieves the additionalProperties setting for the input schema

Parameters:

  • enabled (Boolean, Hash) (defaults to: nil) —

    true to allow any additional properties, false to disallow them, or a Hash for typed additional properties



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# File 'lib/action_mcp/tool.rb', line 257

def additional_properties(enabled = nil)
  if enabled.nil?
    _additional_properties
  else
    self._additional_properties = enabled
  end
end

.annotate(key, value) ⇒ Object 



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# File 'lib/action_mcp/tool.rb', line 96

def annotate(key, value)
  self._annotations = _annotations.merge(key.to_s => value)
end

.annotations_for_protocol(_protocol_version = nil) ⇒ Object

Return annotations for the tool



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# File 'lib/action_mcp/tool.rb', line 126

def annotations_for_protocol(_protocol_version = nil)
  # Always include annotations now that we only support 2025+
  _annotations
end

.call(arguments = {}) ⇒ Object

Class method to call the tool with arguments



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# File 'lib/action_mcp/tool.rb', line 132

def call(arguments = {})
  new(arguments).call
end

.collection(prop_name, type:, description: nil, required: false, default: []) ⇒ void

This method returns an undefined value.

Collection DSL

Defines a collection property for the tool.

Parameters:

  • prop_name (Symbol, String) —

    The collection property name.

  • type (String) —

    The type for collection items.

  • description (String, nil) (defaults to: nil) —

    Optional description for the collection.

  • required (Boolean) (defaults to: false) —

    Whether the collection is required (default: false).

  • default (Array, nil) (defaults to: []) —

    The default value for the collection.

Raises:

  • (ArgumentError) 


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# File 'lib/action_mcp/tool.rb', line 340

def self.collection(prop_name, type:, description: nil, required: false, default: [])
  raise ArgumentError, "Type is required for a collection" if type.nil?

  collection_definition = { type: "array", items: { type: type } }
  collection_definition[:description] = description if description && !description.empty?

  self._schema_properties = _schema_properties.merge(prop_name.to_s => collection_definition)
  new_required = _required_properties.dup
  new_required << prop_name.to_s if required
  self._required_properties = new_required

  # Map the type - for number arrays, use our custom type instance
  mapped_type = if type == "number"
                  Types::FloatArrayType.new
  else
                  map_json_type_to_active_model_type("array_#{type}")
  end

  attribute prop_name, mapped_type, default: default

  # For arrays, we need to check if the attribute is nil, not if it's empty
  return unless required

  validates prop_name, presence: true, unless: -> { send(prop_name).is_a?(Array) }
  validate do
    errors.add(prop_name, "can't be blank") if send(prop_name).nil?
  end
end

.default_tool_name ⇒ String Also known as: default_capability_name

Returns a default tool name based on the class name.

Returns:

  • (String) —

    The default tool name.



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# File 'lib/action_mcp/tool.rb', line 70

def self.default_tool_name
  return "" if name.nil?

  name.underscore.gsub("/", "__").sub(/_tool$/, "")
end

.destructive(enabled = true) ⇒ Object 



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# File 'lib/action_mcp/tool.rb', line 109

def destructive(enabled = true)
  annotate(:destructiveHint, enabled)
end

.destructive? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/action_mcp/tool.rb', line 145

def destructive?
  _annotations["destructiveHint"] == true
end

.execution_metadata ⇒ Object

Returns the execution metadata including task support



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# File 'lib/action_mcp/tool.rb', line 232

def execution_metadata
  {
    taskSupport: _task_support.to_s
  }
end

.idempotent(enabled = true) ⇒ Object 



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# File 'lib/action_mcp/tool.rb', line 117

def idempotent(enabled = true)
  annotate(:idempotentHint, enabled)
end

.idempotent? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/action_mcp/tool.rb', line 141

def idempotent?
  _annotations["idempotentHint"] == true
end

.inherited(subclass) ⇒ Object

Hook called when a class inherits from Tool



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# File 'lib/action_mcp/tool.rb', line 88

def inherited(subclass)
  super
  # Run the ActiveSupport load hook when a tool is defined
  subclass.class_eval do
    ActiveSupport.run_load_hooks(:action_mcp_tool, subclass)
  end
end

.meta(data = nil) ⇒ Object

Sets or retrieves the _meta field



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# File 'lib/action_mcp/tool.rb', line 180

def meta(data = nil)
  if data
    raise ArgumentError, "_meta must be a hash" unless data.is_a?(Hash)

    self._meta = _meta.merge(data)
  else
    _meta
  end
end

.open_world(enabled = true) ⇒ Object 



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# File 'lib/action_mcp/tool.rb', line 121

def open_world(enabled = true)
  annotate(:openWorldHint, enabled)
end

.open_world? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/action_mcp/tool.rb', line 149

def open_world?
  _annotations["openWorldHint"] == true
end

.output_schema(&block) ⇒ Hash

Schema DSL for output structure

Parameters:

  • block (Proc) —

    Block containing output schema definition

Returns:

  • (Hash) —

    The generated JSON Schema



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# File 'lib/action_mcp/tool.rb', line 157

def output_schema(&block)
  return _output_schema unless block_given?

  builder = OutputSchemaBuilder.new
  builder.instance_eval(&block)

  # Store both the builder and the generated schema
  self._output_schema_builder = builder
  self._output_schema = builder.to_json_schema

  _output_schema
end

.output_schema_legacy(schema = nil) ⇒ Object

Legacy output_schema method for backward compatibility



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# File 'lib/action_mcp/tool.rb', line 171

def output_schema_legacy(schema = nil)
  if schema
    raise NotImplementedError, "Legacy output schema not yet implemented. Use output_schema DSL instead!"
  end

  _output_schema
end

.property(prop_name, type: "string", description: nil, required: false, default: nil, **opts) ⇒ void

This method returns an undefined value.

Property DSL (Direct Declaration)

Defines a property for the tool.

This method builds a JSON Schema definition for the property, registers it in the tool’s schema, and creates an ActiveModel attribute for it.

Parameters:

  • prop_name (Symbol, String) —

    The property name.

  • type (String) (defaults to: "string") —

    The JSON Schema type (default: “string”).

  • description (String, nil) (defaults to: nil) —

    Optional description for the property.

  • required (Boolean) (defaults to: false) —

    Whether the property is required (default: false).

  • default (Object, nil) (defaults to: nil) —

    The default value for the property.

  • opts (Hash) —

    Additional options for the JSON Schema.



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# File 'lib/action_mcp/tool.rb', line 309

def self.property(prop_name, type: "string", description: nil, required: false, default: nil, **opts)
  # Build the JSON Schema definition.
  prop_definition = { type: type }
  prop_definition[:description] = description if description && !description.empty?
  prop_definition.merge!(opts) if opts.any?

  self._schema_properties = _schema_properties.merge(prop_name.to_s => prop_definition)
  new_required = _required_properties.dup
  new_required << prop_name.to_s if required
  self._required_properties = new_required

  # Map the JSON Schema type to an ActiveModel attribute type.
  attribute prop_name, map_json_type_to_active_model_type(type), default: default
  validates prop_name, presence: true, if: -> { required }

  return unless %w[number integer].include?(type)

  validates prop_name, numericality: true, allow_nil: !required
end

.read_only(enabled = true) ⇒ Object 



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# File 'lib/action_mcp/tool.rb', line 113

def read_only(enabled = true)
  annotate(:readOnlyHint, enabled)
end

.read_only? ⇒ Boolean

Helper methods for checking annotations

Returns:

  • (Boolean) 


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# File 'lib/action_mcp/tool.rb', line 137

def read_only?
  _annotations["readOnlyHint"] == true
end

.requires_consent! ⇒ Object

Marks this tool as requiring consent before execution



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# File 'lib/action_mcp/tool.rb', line 191

def requires_consent!
  self._requires_consent = true
end

.requires_consent? ⇒ Boolean

Returns whether this tool requires consent

Returns:

  • (Boolean) 


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# File 'lib/action_mcp/tool.rb', line 196

def requires_consent?
  _requires_consent
end

.resumable_steps(&block) ⇒ void

This method returns an undefined value.

Resumable Steps DSL (ActiveJob::Continuable support)

Defines resumable execution steps for long-running tools

Parameters:

  • block (Proc) —

    Block containing step definitions



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# File 'lib/action_mcp/tool.rb', line 244

def resumable_steps(&block)
  self._resumable_steps_block = block
end

.resumable_steps_defined? ⇒ Boolean

Checks if tool has resumable steps defined

Returns:

  • (Boolean) 


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# File 'lib/action_mcp/tool.rb', line 250

def resumable_steps_defined?
  _resumable_steps_block.present?
end

.schema_property_keys ⇒ Object

Returns cached string keys for schema properties to avoid repeated conversions



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# File 'lib/action_mcp/tool.rb', line 271

def schema_property_keys
  return _cached_schema_property_keys if _cached_schema_property_keys

  self._cached_schema_property_keys = _schema_properties.keys.map(&:to_s)
  _cached_schema_property_keys
end

.task_forbidden! ⇒ Object 



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# File 'lib/action_mcp/tool.rb', line 227

def task_forbidden!
  self._task_support = :forbidden
end

.task_optional! ⇒ Object 



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# File 'lib/action_mcp/tool.rb', line 223

def task_optional!
  self._task_support = :optional
end

.task_required! ⇒ Object

Convenience methods for task support



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# File 'lib/action_mcp/tool.rb', line 219

def task_required!
  self._task_support = :required
end

.task_support(mode = nil) ⇒ Symbol

Task Support DSL (MCP 2025-11-25)

Sets or retrieves the task support mode for this tool

Parameters:

  • mode (Symbol, nil) (defaults to: nil) —

    :required, :optional, or :forbidden (default)

Returns:

  • (Symbol) —

    The current task support mode



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# File 'lib/action_mcp/tool.rb', line 206

def task_support(mode = nil)
  if mode
    unless %i[required optional forbidden].include?(mode)
      raise ArgumentError, "task_support must be :required, :optional, or :forbidden"
    end

    self._task_support = mode
  else
    _task_support
  end
end

.title(value = nil) ⇒ Object

Convenience methods for common annotations



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# File 'lib/action_mcp/tool.rb', line 101

def title(value = nil)
  if value
    annotate(:title, value)
  else
    _annotations["title"]
  end
end

.to_h(protocol_version: nil) ⇒ Hash

Tool Definition Serialization

Returns a hash representation of the tool definition including its JSON Schema.

Returns:

  • (Hash) —

    The tool definition.



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# File 'lib/action_mcp/tool.rb', line 375

def self.to_h(protocol_version: nil)
  schema = {
    type: "object",
    properties: _schema_properties
  }
  schema[:required] = _required_properties if _required_properties.any?

  # Add additionalProperties if configured
  add_additional_properties_to_schema(schema, _additional_properties)

  result = {
    name: tool_name,
    description: description.presence,
    inputSchema: schema
  }.compact

  # Add output schema if defined
  result[:outputSchema] = _output_schema if _output_schema.present?

  # Add annotations if protocol supports them
  annotations = annotations_for_protocol(protocol_version)
  result[:annotations] = annotations if annotations.any?

  # Add execution metadata (MCP 2025-11-25)
  # Only include if not default (forbidden) to minimize payload
  if _task_support && _task_support != :forbidden
    result[:execution] = execution_metadata
  end

  # Add _meta if present
  result[:_meta] = _meta if _meta.any?

  result
end

.tool_name(name = nil) ⇒ String

Tool Name and Description DSL

Sets or retrieves the tool’s name.

Parameters:

  • name (String, nil) (defaults to: nil) —

    Optional. The name to set for the tool.

Returns:

  • (String) —

    The current tool name.



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# File 'lib/action_mcp/tool.rb', line 43

def self.tool_name(name = nil)
  if name
    self._capability_name = name
    re_register_if_needed
    name
  else
    _capability_name || default_tool_name
  end
end

.type ⇒ Object 



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# File 'lib/action_mcp/tool.rb', line 79

def type
  :tool
end

.unregister_from_registry ⇒ Object 



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# File 'lib/action_mcp/tool.rb', line 83

def unregister_from_registry
  ActionMCP::ToolsRegistry.unregister(self) if ActionMCP::ToolsRegistry.items.values.include?(self)
end

Instance Method Details

#additional_params ⇒ Object

Returns additional parameters that were passed but not defined in the schema



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# File 'lib/action_mcp/tool.rb', line 435

def additional_params
  @_additional_params || {}
end

#call ⇒ Object

Public entry point for executing the tool Returns an array of Content objects collected from render calls



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# File 'lib/action_mcp/tool.rb', line 441

def call
  @response = ToolResponse.new
  performed = false            # ← track execution

  if valid?
    begin
      run_callbacks :perform do
        performed = true       # ← set if we reach the block
        perform
      end
    rescue StandardError => e
      # Show generic error message for HTTP requests, detailed for direct calls
      error_message = if execution_context[:request].present?
                         "An unexpected error occurred."
      else
        e.message
      end
      @response.mark_as_error!(:internal_error, message: error_message)
    end
  else
    @response.mark_as_error!(:invalid_params,
                             message: "Invalid input",
                             data: errors.full_messages)
  end

  # If callbacks halted execution (`performed` still false) and
  # nothing else marked an error, surface it as invalid_params.
  if !performed && !@response.error?
    @response.mark_as_error!(:invalid_params, message: "Tool execution was aborted")
  end

  @response
end

#inspect ⇒ Object 



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# File 'lib/action_mcp/tool.rb', line 475

def inspect
  attributes_hash = attributes.transform_values(&:inspect)

  response_info = if defined?(@response) && @response
                    "response: #{@response.contents.size} content(s), isError: #{@response.is_error}"
  else
                    "response: nil"
  end

  errors_info = errors.any? ? ", errors: #{errors.full_messages}" : ""

  "#<#{self.class.name} #{attributes_hash.map do |k, v|
    "#{k}: #{v.inspect}"
  end.join(', ')}, #{response_info}#{errors_info}>"
end

#render(structured: nil, **args) ⇒ Object

Override render to collect Content objects and support structured content



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# File 'lib/action_mcp/tool.rb', line 492

def render(structured: nil, **args)
  if structured
    # Validate structured content against output_schema if enabled
    validate_structured_content!(structured) if self.class._output_schema

    # Render structured content
    set_structured_content(structured)
    structured
  else
    # Normal content rendering
    content = super(**args) # Call Renderable's render method
    @response.add(content)  # Add to the response
    content # Return the content for potential use in perform
  end
end

#render_resource_link(**args) ⇒ Object

Override render_resource_link to collect ResourceLink objects



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# File 'lib/action_mcp/tool.rb', line 509

def render_resource_link(**args)
  content = super(**args) # Call Renderable's render_resource_link method
  @response.add(content)  # Add to the response
  content # Return the content for potential use in perform
end