Module: ActionMCP::Server::Resources

Included in:
TransportHandler
Defined in:
lib/action_mcp/server/resources.rb

Instance Method Summary collapse

Instance Method Details

#send_resource_read(id, params) ⇒ Object

Read and return the contents of a resource

Parameters:

  • id (String, Integer) —

    The ID of the request to respond to

  • params (Hash) —

    Parameters specifying which resource to read



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# File 'lib/action_mcp/server/resources.rb', line 47

def send_resource_read(id, params)
  uri = params["uri"]
  template = find_registered_template_for_uri(uri)

  unless template
    error = {
      code: -32_002,
      message: "Resource not found",
      data: { uri: uri }
    }
    send_jsonrpc_response(id, error: error)
    return
  end

  # Check if resource requires consent and if consent is granted
  if template.respond_to?(:requires_consent?) && template.requires_consent? && !session.consent_granted_for?("resource:#{template.name}")
    error = {
      code: -32_002,
      message: "Consent required for resource template '#{template.name}'"
    }
    send_jsonrpc_response(id, error: error)
    return
  end

  unless template.readable_uri?(uri)
    error = {
      code: -32_002,
      message: "Resource not found",
      data: { uri: uri }
    }
    send_jsonrpc_response(id, error: error)
    return
  end

  begin
    # Create template instance and set execution context
    record = template.process(uri)
    unless record
      error = {
        code: -32_002,
        message: "Resource not found",
        data: { uri: uri }
      }
      send_jsonrpc_response(id, error: error)
      return
    end

    record.with_context({ session: session })

    response = record.call

    if response.error?
      send_jsonrpc_response(id, error: response.to_h)
    else
      # Normalize contents to MCP ReadResourceResult shape
      contents = response.contents.map { |c| normalize_read_content(c, uri) }
      send_jsonrpc_response(id, result: { contents: contents })
    end
  rescue StandardError => e
    Rails.logger.error "[MCP Error] #{e.class}: #{e.message}"
    send_jsonrpc_error(id, :internal_error, "Failed to read resource: #{e.message}")
  end
end

#send_resource_subscribe(id, uri) ⇒ Object

Subscribe the current session to updates for an available resource.



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# File 'lib/action_mcp/server/resources.rb', line 112

def send_resource_subscribe(id, uri)
  unless find_registered_template_for_uri(uri)
    send_jsonrpc_response(id, error: resource_not_found_error(uri))
    return
  end

  session.resource_subscribe(uri)
  send_jsonrpc_response(id, result: {})
end

#send_resource_templates_list(request_id, params = {}) ⇒ Object

Send list of resource templates to the client

Parameters:

  • request_id (String, Integer) —

    The ID of the request to respond to

  • params (Hash) (defaults to: {}) —

    Optional params including "cursor" for pagination



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# File 'lib/action_mcp/server/resources.rb', line 29

def send_resource_templates_list(request_id, params = {})
  templates = session.registered_resource_templates.map(&:to_h)
  log_resource_templates

  page, next_cursor = paginate(templates, cursor: params["cursor"])

  result = { resourceTemplates: page }
  result[:nextCursor] = next_cursor if next_cursor

  send_jsonrpc_response(request_id, result: result)
rescue Server::CursorError => e
  send_jsonrpc_error(request_id, :invalid_params, e.message)
end

#send_resource_unsubscribe(id, uri) ⇒ Object

Remove a resource update subscription. Unsubscribing is idempotent.



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# File 'lib/action_mcp/server/resources.rb', line 123

def send_resource_unsubscribe(id, uri)
  session.resource_unsubscribe(uri)
  send_jsonrpc_response(id, result: {})
end

#send_resources_list(request_id, params = {}) ⇒ Object

Send list of concrete resources to the client. Aggregates resources from templates that implement self.list.

Parameters:

  • request_id (String, Integer) —

    The ID of the request to respond to

  • params (Hash) (defaults to: {}) —

    Optional params including "cursor" for pagination



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# File 'lib/action_mcp/server/resources.rb', line 11

def send_resources_list(request_id, params = {})
  all_resources = collect_resources(request_id)
  return unless all_resources # nil means an error was already sent

  page, next_cursor = paginate(all_resources, cursor: params["cursor"])

  result = { resources: page.map(&:to_h) }
  result[:nextCursor] = next_cursor if next_cursor

  send_jsonrpc_response(request_id, result: result)
rescue Server::CursorError => e
  send_jsonrpc_error(request_id, :invalid_params, e.message)
end