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How to add your Anthropic (Claude) key

Claude 3.5 Sonnet, Claude 3.5 Haiku

API key format: sk-ant-api03-… (108 chars)

Anthropic builds the Claude family of models — great for natural, nuanced rewriting.

Stored encrypted. Your key is encrypted with pgcrypto inside our Supabase database the moment you save it. Just like your password, we can’t read it back — only your rewrite requests can decrypt it in-memory to call Anthropic (Claude).

Pricing: Anthropic bills per token. Haiku is the cheapest, Sonnet is the best balance of quality and price.

Step-by-step

  1. Create an Anthropic API account

    Go to console.anthropic.com and sign up with Google or email. You will need to verify a phone number (one number can only be used for one account). This is separate from a Claude.ai chat subscription — the API is its own product and has its own billing.

    Open Anthropic console

  2. Add prepaid credits

    Open Settings → Plans & Billing → ‘Buy credits’. Minimum top-up is $5. API access is gated on a positive balance — keys silently return 400 errors without credits. While here, set a monthly spend limit under ‘Usage limits’.

    Plans & Billing

  3. Open the API keys page

    Click your workspace name → Settings → ‘API keys’ in the left sidebar.

    API keys page

  4. Create a new key

    Click ‘Create Key’. Name it ‘PulseWrite’. Workspace: ‘Default’ (or a dedicated one). Permissions: leave as ‘All’ — Anthropic does not yet offer scoped read-only keys for inference.

  5. Copy the key (starts with sk-ant-api03-…)

    Anthropic shows the full key exactly once in a modal — copy it immediately. If you close the modal without copying, you must delete it and create a new one.

  6. Paste it into PulseWrite

    Dashboard → Your AI keys → choose ‘Anthropic (Claude)’ and paste. Save.

    Open dashboard

Tips

  • Claude 3.5 Haiku ($0.80/$4 per 1M tok) is the cheap default for short rewrites.
  • Claude 3.5 Sonnet ($3/$15 per 1M tok) produces noticeably more natural prose — worth it for long emails.
  • Pricing: anthropic.com/pricing. Free trial credits are usually granted automatically after phone verification.
Open Anthropic (Claude) console Go to my dashboard

Anthropic (Claude) FAQ

Is a Claude.ai subscription enough?

No. The web app and the API are billed separately — you need a console.anthropic.com account with prepaid API credits.

Why does the API return 400 right after I add my key?

Almost always a $0 balance. Add credits under Plans & Billing and the same key starts working immediately.

Which Claude model should I pick for rewriting?

Claude 3.5 Haiku for cheap, fast rewrites; Claude 3.5 Sonnet when you want noticeably more natural prose on longer text.

Other providers

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