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Hjarni for AI agents

Hjarni is a personal knowledge management platform for organizing, searching, and linking notes and tags. Individuals and small teams use it to keep this organized without extra manual upkeep. Connect it once through Arc0, and your agent, or Claude, ChatGPT and Cursor, can use it through one MCP endpoint, limited to what each user approved.

Connect HjarniSee the 15 actions ↓
ProductivityAPI keyMCP + RESThjarni.io
AUDIT LOG · HJARNIPOLICY: acme-support
09:41:07 · claude · u_8f2read
hjarni.list_tags
List Tags✓ allowed · 212ms
09:41:08 · claude · u_8f2read
hjarni.get_note
Get Note✓ allowed · 164ms
09:41:09 · claude · u_8f2write
hjarni.create_tag
Create Tag✓ approved · approved by user
09:41:12 · claude · u_8f2destructive
hjarni.trash_note
Move Note to Trash✕ blocked · policy: deny
EVERY HJARNI CALL, ON THE RECORD
01 · USE CASES

What agents do in Hjarni.

01

Create a note

Save a new note with content and tags from a conversation or research session.

02

Search notes by tag

Search notes tagged to a topic to gather background before writing a summary.

03

Restore a trashed note

Restore a note from the trash only after the user confirms it was deleted by mistake.

02 · ACTIONS

15 Hjarni actions, graded by risk.

Every Hjarni action is tagged read, write or destructive, so one policy covers the whole app and new actions inherit the right default.

read

6

Look things up. Allowed by default.

  • hjarni.get_note
    Get Note
  • hjarni.list_tags
    List Tags
  • hjarni.list_notes
    List Notes
  • hjarni.list_containers
    List Containers
  • hjarni.get_account_status
    Get Account Status
  • hjarni.list_trashed_notes
    List Trashed Notes

write

8

Create and change things. Allow, or ask the user first.

  • hjarni.create_tag
    Create Tag
  • hjarni.create_note
    Create Note
  • hjarni.update_note
    Update Note
  • hjarni.create_notes
    Create Notes
  • hjarni.create_container
    Create Container
  • hjarni.update_container
    Update Container
  • hjarni.rename_tag
    Rename Tag
  • hjarni.restore_note
    Restore Note

destructive

1

Delete, cancel or archive. Ask first, or deny outright.

  • hjarni.trash_note
    Move Note to Trash
03 · HOW IT WORKS

Hjarni in three steps.

  1. 01Your users connect HjarniThey add their Hjarni api key on Arc0 Connect, under your brand. It goes straight into the vault.
  2. 02You set the rulesReads run, writes like “create Tag” can wait for the user, and “move Note to Trash” can be denied outright.
  3. 03Any agent can actYour agent calls Hjarni through the Arc0 SDK or MCP, and so can Claude, ChatGPT and Cursor. Every call lands on the audit log.
POLICY.TS
await arc0.policies.set('hjarni', {
  read: 'allow',
  write: 'ask',        // create_tag
  destructive: 'deny',  // trash_note
})

# Claude Code: the same connection, one URL
$ claude mcp add --transport http arc0 \
    https://mcp.arc0.ai/u/u_8f2
04 · AUTH AND DATA

How Hjarni connects.

Users add their Hjarni api key on Arc0 Connect. It is encrypted in the vault, never shown to the model, and each user can rotate or revoke it at any time.

The same Hjarni connection serves your agent over MCP and your own backend over REST and the proxy, so a user connects once. How Arc0 handles credentials →

AUTH
API key
CREDENTIALS
Per-tenant encrypted vault
MODEL SEES
Results only, never credentials
AUDIT LOG
Every call, on every plan
05 · WORKS WITH

Use Hjarni from any agent.

Claude
ChatGPT
Cursor
Codex
VS Code
OpenAI Agents SDK
Claude Agent SDK
Vercel AI SDK
Mastra
LangGraph
06 · RELATED

More productivity apps.

Notion57 actionsAirtable27 actionsConfluence70 actionsClickUp164 actionsAmazing Marvin10 actionsRentman130 actionsHub Planner122 actionsCoda110 actions
ALL PRODUCTIVITY APPS →
07 · FAQ

Hjarni and Arc0, answered.

Q01

Can I use Hjarni with Claude, ChatGPT or Cursor?

Yes. Connect Hjarni to Arc0 once, then add your Arc0 MCP URL to Claude, ChatGPT, Cursor, Claude Code or any other remote-MCP client. Each assistant only gets the Hjarni actions you allow.

Q02

How do users connect Hjarni?

Users add their Hjarni api key on Arc0 Connect. It is encrypted in the vault, never shown to the model, and each user can rotate or revoke it at any time.

Q03

Which Hjarni actions can my agent take?

15 in total: 6 read, 8 write and 1 destructive, such as “create Tag”. Your policies decide which of them each agent may call.

Q04

Can I stop my agent from deleting things in Hjarni?

Yes. Actions like “move Note to Trash” are graded destructive. Set destructive actions to deny, or to ask so the user approves each one, and blocked calls still show up on the audit log.

Q05

Can my own backend call Hjarni too?

Yes. The same Hjarni connection is available over REST and through the Arc0 proxy, so your product and your agent share one connection per user.

Get started

Plug Hjarni into your agent.

Your users connect Hjarni once, under your brand. Your agent gets 15 actions behind your policies, with every call on the record.

Connect HjarniBrowse all apps →

Free to build · MCP + REST · Audit log on every plan