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

Examples:

Input:

id = "req-789"
params = { uri: "file:///example.txt" }

Output:

# Sends: {"jsonrpc":"2.0","id":"req-789","result":{"contents":[{"uri":"file:///example.txt","text":"Example content"}]}}

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 = ResourceTemplatesRegistry.find_template_for_uri(uri)

  unless template
    send_jsonrpc_error(id, :method_not_found, "No resource template found for URI: '#{uri}'")
    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}")
    # Use custom error response for consent required (-32002)
    error = {
      code: -32_002,
      message: "Consent required for resource template '#{template.name}'"
    }
    send_jsonrpc_response(id, error: error)
    return
  end

  begin
    # Create template instance and set execution context
    record = template.process(uri)
    record.with_context({ session: session })

    response = record.call

    if response.error?
      # response.to_h works properly when error? is true:
      send_jsonrpc_response(id, error: response.to_h)
    else
      # Handle successful response - ResourceResponse.contents is already an array
      send_jsonrpc_response(id, result: { contents: response.contents.map(&:to_h) })
    end
  rescue StandardError => e
    # Should rather `ErrorHandling` module be included here? Then we could use `log_error(e)` directly.
    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_templates_list(request_id) ⇒ Object

Send list of resource templates to the client

Examples:

Input:

request_id = "req-456"

Output:

# Sends: {"jsonrpc":"2.0","id":"req-456","result":{"resourceTemplates":[{"uriTemplate":"db://{table}","name":"Database Table"}]}}

Parameters:

  • request_id (String, Integer) —

    The ID of the request to respond to



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# File 'lib/action_mcp/server/resources.rb', line 28

def send_resource_templates_list(request_id)
  templates = ActionMCP::ResourceTemplatesRegistry.resource_templates.values.map(&:to_h)
  # TODO: add pagination support
  # TODO add autocomplete
  log_resource_templates
  send_jsonrpc_response(request_id, result: { resourceTemplates: templates })
end

#send_resources_list(request_id) ⇒ Object

Send list of available resources to the client

Examples:

Input:

request_id = "req-123"

Output:

# Sends: {"jsonrpc":"2.0","id":"req-123","result":{"resources":[]}}

Parameters:

  • request_id (String, Integer) —

    The ID of the request to respond to



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# File 'lib/action_mcp/server/resources.rb', line 15

def send_resources_list(request_id)
  send_jsonrpc_response(request_id, result: { resources: [] })
end