What phrase indicates writing as a representative of someone else?

The phrase "on behalf of my client" clearly indicates that the writing is being done as a representative of someone else, specifically a client. This expression emphasizes that the author is acting in the interest or with the permission of another party, highlighting a formal relationship where the writer is tasked with conveying the client's views or needs. This is commonly used in professional contexts where individuals or organizations might write letters, reports, or other documents to represent another individual’s or entity’s opinions or requests.

The other options do not convey this idea effectively. "For my own interests" suggests a focus on the writer's personal agenda, while "in my own words" emphasizes individual expression, which is not about representation. "For another's benefit" might imply consideration for someone else but lacks the specific clarity of representing or advocating for that person's views directly.