What happened
I was building a small tool for myself. It reads my PDFs and photos and pulls out the numbers so I don't have to type them in.
The AI building it set it up on a separate pay-per-use AI account. New account, new key, a new bill every month. It had already started on that setup.
I stopped it. I already pay for Claude Code every month, and I'm the only person who will ever use this tool. So why pay twice?
We switched it to run on my subscription. No new account, no new key, no surprise bill.
Before and after
- Before: a second AI account, a new key to keep safe, a cost per document.
- After: it runs on the plan I already pay for. One less account, one less key.
The catch - read this part
This only works if it's just you.
Anthropic's terms say you can't share your account or let anyone else use it. So the moment your staff, a client or a partner uses the tool, it needs its own paid setup. Mine is just me, so it fits.
And this is how it works as of October 21, 2026. Anthropic's own help page says you can use the Agent SDK and claude -p with your subscription, and it counts against your plan's usage limits. They've announced changes to this before, then paused them, so it can change again. Check their pages before you build on it:
https://support.claude.com/en/articles/15036540-use-the-claude-agent-sdk-with-your-claude-plan
https://www.anthropic.com/legal/consumer-terms
Update - November 2026
Since late October, Anthropic also gives some subscribers monthly API credits, on top of the plan. Mine is $200 a month. Per Anthropic's page: Max gets $100 a month, Ultra (what used to be Max 20x) gets $200, and Pro and Free get none.
What they cover: the Claude API, the Agent SDK and Managed Agents. What they don't cover: Claude Code. They reset every billing cycle and don't roll over. When they run out, your requests stop until next month, unless you've bought more credit.
So the question changes. It's no longer "my subscription or a new paid account?" It's "my subscription, or the credits I already get?" Either way, check before you pay for anything new.
Check Anthropic's page first: https://platform.claude.com/docs/en/about-claude/api-credits-for-subscribers
Something to steal
Before your AI sets up a new paid account for a tool, ask it this:
Who will use this tool - only me, or other people too? If only me, can it run on the subscription I already pay for? Show me the vendor's own page that says so.
If it can't show you the page, don't take its word for it.