A lot of people now connect Claude to Obsidian or Notion over MCP and call it a second brain. That works well for notes. A personal assistant, though, spends most of its day on three questions: what's due, what am I skipping, and what did I actually do? Those answers live in to-dos, dailies and habit counts, which a notes vault doesn't really hold.
I built Gnothi with those in it, and it has an MCP server, so Claude can read and change them from any chat. I also made Habitica, and Gnothi's habits, dailies and rewards follow its design, with the game turned down. It's my product, so weigh the comparison accordingly. The setup steps are at the end.
It's a store outside Claude that Claude can read and write through an MCP connector. Your notes, tasks and history live there, so a chat on your phone, a Cowork session and a Claude Code terminal all work from the same list. Whether that's worth setting up depends on what you put in it. If Claude only ever reads your notes, you'd get most of the value from search. Where it starts to pay off is when Claude keeps the list for you: adds what you mention, checks off what you finish, and tells you what to do with the twenty minutes you have.
| What Claude works with | How Claude connects | Watch app | |
|---|---|---|---|
| Obsidian | Markdown files in a vault folder | Claude Code can read the folder directly; MCP servers are community projects | No official one; it's a long-standing forum request |
| Notion | Pages and databases | Notion's hosted MCP server, with OAuth | No official one I could find; third-party apps send notes to it |
| Workflowy | One infinitely nested outline | Community MCP servers built on Workflowy's API | None I could find |
| Gnothi | To-dos, dailies, habits, rewards and tracked numbers, an outline under each, and an optional journal | Hosted MCP server, with an API key you scope | Apple Watch and Wear OS |
Obsidian and Notion are better homes for long-form writing, wikis and project docs. If that's your second brain, keep it, and add Gnothi for the part they aren't built around: the running list of what's due and the log of what you did.
Many people looking for a second brain with Claude start with Obsidian, for good reason. Your notes are plain Markdown files on your own disk, nothing is locked in, and there's a community plug-in for almost anything. If you like owning your files and tinkering, it's a great home. Here's what it takes to make it Claude's to-do list and habit tracker:
Each step is documented somewhere, but that's a lot of wiring before Claude checks off its first to-do, and the system in step 5 is yours to maintain.
Notion is shorter. Its hosted MCP server signs in with OAuth and works wherever Claude does, so there's nothing to sync or bridge. You still design the to-do and habit databases yourself, or start from a template.
Gnothi is hosted and built for this, so there's no sync to wire up and no system to design. Make a key in Gnothi, add one custom connector on claude.ai, and paste the setup prompt from Gnothi's "Use with Claude" panel into a new chat. Claude asks a few questions (what you want done, which habits you want, what you'd like to keep an eye on), shows you the whole board as a dry run, and builds it once you say yes. It's a few minutes of clicking and one conversation.
Every Gnothi field has a Workflowy-style outline under it: infinite nesting, Alt+↓ to zoom into a node and Alt+↑ to zoom back out, breadcrumbs, mirrors, file attachments up to 10 MB, and OPML and Markdown import and export. Workflowy exports OPML, so an existing outline comes over.
Any item can carry a due date. Gnothi labels it in words ("due today", "3d overdue") and colors it by how close it is, and any item can repeat every N days. Overdue costs nothing in the game, so the to-do you forgot two months ago doesn't wipe out your points.
What it looks like day to day, from Gnothi's Claude page:
Claude checks off what's done. Anything stale, like tickets for a concert that's already passed, gets set aside for you to decide, and nothing is deleted until you say yes. An item changed or deleted by mistake can be restored for about 30 days.
Each field has a Notes box. Write how you want it kept ("anything with a phone call goes under Calls"), and Claude reads that as your preferences. With Cowork, or Claude Pro or Max, Claude can also set up an optional morning brief or nightly triage as a scheduled task.
Urge surfing is G. Alan Marlatt's term. When an urge shows up, you notice it, watch it build and peak, and wait for it to fade without acting on it, like a wave passing under you.
Most habit trackers give you one habit per urge: cigarettes, doomscrolling, late-night games. I keep a single catch-all habit instead; call it Urge surf. Whatever the urge is, there's one moment that decides it: I either surf it or give in. Surfing it gets a +1, and giving in gets a −1. Smoke a cigarette, minus. Feel the pull to smoke and ride it out, plus.
Mine is named "dream check," because my way of surfing starts with a lucid dreamer's reality check: before anything else, I check whether I'm in a dream, and that pause is where the urge gets a chance to pass.
The physical versions of this idea have been around for years: snapping a rubber band on your wrist, or Pavlok, a crowdfunded wristband that shocks you. Those make giving in hurt. On a watch it becomes a data point instead: one tap at the moment it happens, and every +1 and −1 adds up over weeks.
Gnothi runs on Apple Watch and Wear OS. You pick one habit as your watch face habit, and it gets a pair of complications:
That's why one umbrella habit suits the watch so well: there's a single watch face slot, and every urge goes to the same two buttons. A tap counts even when the watch is offline, and it sends once it's back. Taps on the watch, logging and check-offs all work with AI off.
Watch apps are uncommon here. None of the other second-brain tools in the table above has an official one. The +/− habit itself is old Habitica design, now one tap from the watch face.
A +1/−1 habit is a number per day, so it goes everywhere Gnothi's other fields go:
The watch's Do it button is the assistant part. Tap it and say "dentist appointment 3pm Saturday," and it goes on your to-dos, due Saturday. "Done" plus an item's name checks it off. You can log a value the same way, or buy a reward after a confirm. Gnothi's rewards are treats you price in points and buy with what your habits and dailies earned. Do it is an AI call, so it needs AI on and uses a little of your credits.
There's a Do it complication too. On Wear OS, a second launcher icon, "Gnothi Do it", can go on a hardware button (Settings → Gestures → Customize buttons), so adding a to-do is one press and a sentence.
https://api.gnothiai.com/mcp. Under the connector's request headers, add Authorization: Bearer followed by your key.claude mcp add --transport http gnothi https://api.gnothiai.com/mcp --header "Authorization: Bearer gnk_..." --scope user
Use a personal Claude account. On a Team or Enterprise account, everyone in the organization would share your key. API keys are free to make and use. For the watch, install the Gnothi phone app from the App Store or Google Play, then go to Account → Security → Connect watch.
If you're coming from Habitica, how I use Habitica covers its habits, dailies and rewards, which work much like Gnothi's.