A professional summary is the fastest way to tell a hiring manager what kind of worker this person is. If the summary is vague, the rest of the resume has to work twice as hard.
When you sit with a client on this section, you are doing two jobs: framing their trajectory, and putting scan-friendly proof at the top of the page.
What to include
Prefer numbers that show scope: years in the field (usually cap this at 15+ to reduce age bias), budget, caseload, team size, revenue, or placement volume. Qualitative proof can work too: named clients, sectors, or populations, if it matches the posting.
If they have fewer than five years of experience, lead with training, internships, and the strongest outcomes they do have, not empty adjectives.
What to leave out
This is not a career objective. Do not let the summary say what they want. Have it say what they can do. Cut filler like motivated and hard-working.
How to format it
Keep it at the top. Bullets usually scan better than a dense paragraph, especially when each line carries a number or a sector.
If applications are stalling, reread the summary against the posting before you rewrite the whole resume. A specific, evidence-heavy opener often changes who gets a callback.