Use of broader principles of research underscored by philosophical rationales is termed as:

The correct option is Research Methodology.

Explanation:
Research methodology refers to the systematic and theoretical analysis of the methods applied to a field of study. It encompasses the broader principles, theoretical frameworks, and philosophical rationales (such as ontology and epistemology) that guide the overall research design. Rather than just focusing on the mechanics of data collection, methodology explains and justifies why specific methods, tools, or techniques are chosen and how they align with the philosophical assumptions of the research.

Let us compare this with the other options to understand the distinction:
- Research Tools: These are the physical or digital instruments used to collect or analyze data (e.g., questionnaires, scales, interview schedules, or statistical software).
- Research Techniques: These are the specific, step-by-step procedures and behaviors utilized to execute a research design (e.g., conducting a semi-structured interview, running a laboratory experiment, or performing a content analysis).

Since the question specifically refers to the use of broader principles underscored by philosophical rationales, Research Methodology is the most appropriate term.