when-free

when-free

Someone asks when you're free. This reads your calendar and gives you the answer, ready to paste.

• Paste the message, get the slots. It reads "Tuesday or Wednesday next week, between 10am and 4pm" and answers for exactly those days and hours.
• Works with Google, Outlook and iCloud calendars, or any .ics file. Several calendars at once.
• Private. It runs on your computer, needs no account and no API key, and never changes your calendar.
• Works from your AI tools too: Claude, Cursor and other MCP clients, Open WebUI, n8n, Shortcuts, scripts.
• And on your other devices: phones, tablets and watches, Home Assistant (and Alexa, Google Home, Siri through it), and the menu bar or status bar of macOS, Linux and Windows.

Contents

Try it · Add your calendar · Everyday use · Reading a message · Use it from other tools · Other devices · Privacy · Settings · What counts as busy · Limits · Problems · Where it is listed

Try it in a minute

With uv, nothing to install first:

uvx when-free demo

To keep it (needs Python 3.11 or newer):

uv tool install when-free          # or: pipx install when-free

whenfree demo

Using Claude Desktop? You can skip all of this: install the one-click extension.

whenfree demo makes up a calendar for next week and answers a recruiter's message from it. It reads none of your data and saves nothing:

  > Hi! Thanks for applying. Could you share a few times on Tuesday, Wednesday or Thursday next week,

between 10am and 4pm? The interview takes about an hour.

Free between 10:00 and 16:00 (Europe/London), slots of 60+ minutes, 15-minute buffer around events:

• Tue 13 Oct: 11:45–12:45, 14:15–16:00
• Wed 14 Oct: 12:15–14:15
• Thu 15 Oct: 13:15–14:45

Add your calendar

1. Copy your calendar's private address. It's a link that ends in .ics:

1. Run `whenfree add` and paste it. The address isn't shown while you paste. It's checked first, and saved only if it works:

   $ whenfree add

Paste the address and press Enter (it is not shown): Added 'personal': 412 events, 9 block time in the next 14 days. Saved in /Users/you/.config/when-free/config.toml, readable only by you. Now run: whenfree

1. Run `whenfree`. You'll see your free time for the next working days.

On a Mac, pbpaste | whenfree add takes the address straight from the clipboard.

Keep the address secret. It works like a password: anyone who has it can read that calendar. Give it to whenfree add and to nothing else, so not to a chat, a shell command or a repository. If it leaks, reset it in your calendar's settings.

Google Calendar, step by step

Do this in a browser, because the phone app doesn't show the address.

1. Open Google Calendar settings: the gear icon, then Settings.
2. In the left column, under Settings for my calendars, click the calendar you want. The one with your own name is where invitations arrive.
3. Scroll down to Integrate calendar and copy Secret address in iCal format. It ends in basic.ics. Don't take "Public address in iCal format", which only works for a calendar you've made public.
4. Run whenfree add and paste it when asked.

No "Secret address"? Work and school accounts can have it switched off. Export the calendar instead (Settings → Import & export → Export), unzip it, and run whenfree add ~/calendars/work.ics. An export is a snapshot, so export again when your calendar changes.

More than one calendar

A slot counts as free only if it's free in every calendar you add.

whenfree add --name work                 # a second calendar: asks for its address

whenfree add ~/calendars/family.ics # an exported file instead of an address whenfree check # can every calendar be read?

They're kept in ~/.config/when-free/config.toml, one [[calendar]] block each, with a name and a url or path. You can edit that file by hand. whenfree init creates an empty one.

Everyday use

Only the slot lines go to standard output. The context goes to standard error, so | pbcopy copies exactly what you'd paste into a reply.

Reading a message

--message finds the days and hours in ordinary text. It understands:

• Dates written in any common way: Thu 1 Oct · Thursday the 1st of October · Monday, October 5th · 5 October · 2026-10-05 · Wednesday 30th
• Hours: between 10:00am and 4:00pm · 10:00–16:00 · 9-5pm · 2 to 4 pm
• Words, when there's no date (here, today is Thursday 1 Oct):

It always tells you how it read the dates, so you can check them against the message. A few rules keep it from guessing:

• Explicit dates win. A heading like "Next week:" above "Wednesday 30th, Thursday 1st" doesn't add a whole week.
• "Good morning" is a greeting, not a time.
• Days already past are left out and named, never dropped silently. "Wednesday 30th" means the nearest Wednesday that's a 30th, so a message from last week reads as last week.
• Words count from today. For an older message that says "tomorrow", give the days yourself with --days.

when-free never connects to your mailbox. You paste the message, pipe it in, or save it to a file.

Let your own language model read the message

If you run a model yourself, it can do the reading instead. Add this to the settings file:

[extract]

command = ["ollama", "run", "llama3.2"] # the prompt is sent on standard input

command = ["my-cli", "ask", "{prompt}"] # or placed where {prompt} is

The command receives the message and must print JSON: {"days": ["2026-10-05"], "hours": "10:00-16:00", "minutes": 60}. If it fails, pattern matching is used instead. Nothing runs unless you configure it, and --no-extract skips it for one run. The message goes to whatever that command talks to, so use a local model for private text.

Use it from other tools

Every way gives the same answer, only reads, and leaves event titles out unless asked.

Claude Code plugin

The plugin bundles the MCP server with a skill that tells Claude when to use it: when you ask about your availability, paste a message asking when you can meet, or before it proposes a time.

/plugin marketplace add YauhenBichel/when-free

/plugin install when-free@when-free

Then add your calendar once, if you have not yet: uvx when-free add.

MCP: Claude, Cursor and other assistants

claude mcp add when-free -- uvx when-free mcp          # Claude Code

For Cursor and other MCP clients, add this to their server list. uvx fetches when-free the first time, so there's nothing to install:

{

"mcpServers": { "when-free": { "command": "uvx", "args": ["when-free", "mcp"] } } }

If you installed it with uv tool install, use "command": "whenfree", "args": ["mcp"] instead. It's also listed in the MCP registry as io.github.YauhenBichel/when-free, on mcprush and in the M8ven Trust Index.

Then just ask: *"Here's the recruiter's message. Which of those times can I do?"* The assistant calls free_slots and answers from your real calendar.

If a tool can't do its job, the assistant gets an error it can read ("could not read the calendar 'work'"), never a guess.

HTTP: Open WebUI, n8n, Shortcuts and scripts

whenfree serve                    # http://127.0.0.1:8765, only reachable from this computer

curl -H "Authorization: Bearer $(cat ~/.config/when-free/token)" \

'http://127.0.0.1:8765/free_slots?days=next%20week&hours=afternoon'

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