How to Use Claude 3.5 Sonnet for Writing and Code
Claude 3.5 Sonnet arrived in June 2024 and quickly became the model writers and developers reached for by default. It is the middle of Anthropic’s three-tier line — below Opus, above Haiku — and it is fast, good with long documents and unusually steady at structured output.
Newer Claude models have since shipped, but 3.5 Sonnet remains common in production because it is cheap and predictable. Plenty of teams still run it as their daily driver.
What Is Claude 3.5 Sonnet Best At?
Three things. Long-context reading — feed it a 100-page report and ask for a structured summary. Writing that sounds less like a chatbot. And code, where it tends to produce readable diffs rather than clever one-liners you have to untangle.
It is weaker on heavy math and on tasks that need multi-step planning, where a reasoning model pulls ahead.
How Do You Get Started?
- Use it at claude.ai on the free tier or via Anthropic’s API for automation.
- Put your long document at the top of the prompt and ask for a specific deliverable.
- For code, give existing style: “Match the style of the file below.”
- Keep separate threads per task — context matters more than people expect.
Anthropic’s console also lets you compare a prompt across model tiers before you commit to one in an app.
How Much Does Claude 3.5 Sonnet Cost?
On claude.ai it is available on the free plan with limits; Pro is about $20/month with higher usage and access to more models. API pricing is per token and cheaper than the top tier, which is why it ends up in a lot of production pipelines where Opus would be wasteful.
When Should You Use a Different Model?
Pick Claude 3.5 Sonnet for writing, summarising and everyday code. For hard reasoning, frontier math, or when you need the absolute best answer and cost is secondary, a top-tier or reasoning model wins. A fair comparison is to run Claude 3.5 Sonnet and one newer model on the same five prompts before you pick.
Key Takeaways
- Claude 3.5 Sonnet (June 2024) is Anthropic’s mid-tier model: fast, cheap, long-context.
- Free tier on claude.ai with caps; Pro ~$20/month; API per-token below the top tier.
- Best for long-document reading, natural writing and readable code.
- Switch to a reasoning or top-tier model for hard multi-step problems.
