The role of the description inside an RSA
In a responsive search ad, headlines are the head and descriptions the body. You load up to 4 descriptions of 90 characters each, and Google shows 2 at a time. The description's job is to confirm user intent and give the final push before the click. Headline attracts, description closes.
That means each description must add something new. If the headline says "Online English Course | 6 Months", the description shouldn't say "Online English course in 6 months with expert teachers". It must add proof, detail, guarantee or an additional benefit.
The 4 descriptions, well distributed
- Description 1 — Detailed benefit: "Speak English with confidence in 6 months. Method validated by 5,000+ students."
- Description 2 — Proof or authority: "Certified native teachers. 4.8★ on verified Google reviews."
- Description 3 — Guarantee or friction-reducer: "Try 7 days free. No card needed. Cancel anytime."
- Description 4 — CTA with soft urgency: "Book your trial now. Limited monthly availability."
The 90-character limit and how to use it
90 characters give more room than a headline but less than it seems. A good description is one short sentence and an even shorter one. Structure: claim + support. "Speak fluently in 6 months. Method validated by 5,000+ students." (63 chars + margin).
Common errors using the 90 chars: cramming two unrelated benefits, padding with adjectives, weird punctuation to fill space.
How Google combines headlines and descriptions
Google shows 3 headlines + 2 descriptions per RSA at a time. The choice is not random: the system tests combinations and prioritizes those with better CTR for the context. If your 4 descriptions are interchangeable, Google learns nothing. If each has a different angle (benefit, proof, guarantee, CTA), the system can pair the right description with the right headline for each search.
What Google allows and doesn't in descriptions
Google rejects descriptions with:
- Excessive caps: "MAKE MONEY NOW" — rejected in review.
- Strange punctuation: "!!!", "???" — limited to one per sentence.
- Non-standard symbols: ★★★★★, ✅ in excess.
- Unverifiable absolute claims: "100% guaranteed", "world's best" without backing.
- Personal info: phones, emails (go in extensions, not in text).
How to write a description that confirms intent
When someone searches "online english course" and your headline says "Online English Course | 6 Months", the ideal description doesn't repeat that. It must confirm it's what the user wants and answer a possible objection. Three patterns that perform:
- "Answer to objection" pattern: "No card. No contracts. Try 7 days free."
- "Specific proof" pattern: "5,000+ certified students. 4.8★ on Google Reviews."
- "What's included" pattern: "Live classes + platform + certificate. All from $19/month."
Common mistakes that hurt conversion
- Repeating the headline in the description: the user just read it.
- No CTA: at least one of the 4 descriptions must close with a specific CTA.
- Vague promises: "The best option in the market" without backing.
- Heavy keyword stuffing: "Online english course english course best english course" — Google penalizes.
- Forgetting strategic pinning: if you want a disclaimer to always appear, pin it to position 1 or 2.
Pinning: when to use and when not
Google allows pinning headlines and descriptions to specific positions. When it pays off:
- Regulatory disclaimers: finance, health, insurance — pin to fixed position.
- Brand-critical description: if a description contains the main offer and you want it guaranteed.
- When NOT to pin: most cases. Pinning blocks algorithm optimization. Pin only what's essential.