Who it is for
Someone who reads a lot, keeps the good bits, and wants a weekly newsletter out of it — without the Saturday morning being a scramble.
The editorial desk
Six things,
Saturdays.
Links pile up all week. On Saturday morning, something good goes out. Curio is the half of a newsletter that is not sending: capturing the links, triaging them, drafting the blurbs, assembling the issue, getting it reviewed. It hands the finished issue to Herald.
Curio owns what goes in the issue. Herald owns who receives it.
Curio in four numbers
8Ways in, one inbox
7Stages, capture to measure
32MCP tools for assistants
0Of them can send
The problem it removesThe hard part was never the writing.
The hard part was never the writing.
It was the collecting.
Saving a link usually means opening an app and pasting a URL, so half of what you meant to keep is never kept at all. Then Saturday morning is a scramble through forty browser tabs and a Notes file.
What it replaces
The tab graveyard, the scratch file, the message you sent yourself, and the forty minutes of re-finding on the morning you meant to write.
What it never touches
Your subscribers. Curio stores the id of a Herald mailing list and nothing else about the people on it.
The pipeline
Seven stages, one direction.
A link enters at the left and leaves as a paragraph somebody read. Every stage is designed for the person clearing sixty items in ten minutes, not for a demo.
Capture
Eight paths in, one inbox, deduplicated on arrival.
Read
Title, author, publication, reading time, and the article's own text, fetched in the background.
Triage
j, k, 1–9, x, u. A hundred items without touching the mouse.
Compose
Several newsletters, each with its own sections, schedule, template and voice.
Draft
A first pass written from why you kept it — never the last word.
Publish
Deliberate, reviewed, and impossible to send twice.
Measure
Which of the six things you sent did people actually open?
CaptureEight ways in.
Eight ways in.
You should never have to open the app to save something.
Competitors ship a browser extension and call capture solved. Curio treats it as the actual problem. Every path below lands in the same inbox and deduplicates against everything already there.
Bookmarklet
shippedOne click from any page in any browser.
Chat message
shippedPost a link in a Chirp channel; the sentence around it becomes the note.
An assistant
shippedClaude, or any MCP client, captures on your behalf — with the reason attached.
Watched feeds
shippedRSS and Atom entries arrive as suggestions, in their own lane.
A capture key
shippedA named, revocable key for Shortcuts, Raycast, Alfred or curl.
Share sheet
comingWill share from Safari, X, your feed reader or Mail — offline included.
Email forwarding
comingA private address of your own; every link in what you forward will be captured.
Browser extension
comingA keyboard shortcut and a right-click menu, to come.
shipped running and covered by tests
building specified and in progress
coming designed, not started
The line Curio does not crossCurio owns what goes in the issue.
Curio owns what goes in the issue.
Herald owns who receives it.
This is the shape of the product, not a limitation of it. Opt-in, unsubscribes, bounces and deliverability live in one place rather than two.
- Never holds a subscriber
- Curio stores the id of a Herald mailing list and nothing else about the people on it. A list you do not own cannot appear, because Herald decides that, not Curio.
- Never renders email HTML
- Curio emits Markdown; Herald turns it into email-safe HTML with the same renderer its sends use. Which is why the preview in Curio is the real artifact rather than an approximation of one.
- Never sends
- Curio hands Herald a draft and asks it to schedule or send. Assembly is automated; sending never is.
Agents, up to a pointAn assistant can take an issue
An assistant can take an issue
right up to the moment it is ready.
Curio exposes its whole workflow over the Model Context Protocol: 32 tools covering capture, triage, publications, feeds, issue assembly, blurb drafting and preview.
- And then it stops. There is no tool that sends, schedules or test-sends, and a test enforces that as the surface grows.
- An agent may prepare a send; a person performs it. In a market racing toward hands-free publishing, declining to automate the irreversible step is a position, not an omission.
- Every capture carries its reason. An assistant saving a link on your behalf attaches why, and that note outranks the article's own blurb everywhere downstream.
An assistant, mid-week
___PRESERVE_BLOCK_7___
Four things that are different
Not a summarizer with an inbox bolted on.
One link, several newsletters, different words
Most tools tie a saved link to one newsletter. In Curio the blurb belongs to the issue, not the link — so the same article can run in two publications and read completely differently in each.
Eight ways in, not one
A share sheet, an email address, a chat channel, an assistant, watched feeds, a key for scripts. Capture is the friction; a single extension does not remove it.
The note is the product
The sentence you write when you save something is the highest-value field in the system, and everything downstream is built around it. That is a different premise from “paste a URL, get a summary.”
It will not send on its own
Curio assembles automatically and never sends automatically. A crash halfway through publishing cannot produce a duplicate send.
Worth saying out loud
What you saved is yours.
Nothing is deleted behind your back
Nothing captured is ever removed by a background process. Feed suggestions age out, reversibly, and that is the only automatic tidying that happens.
Fetching is careful
Curio fetches pages you have chosen to read; it does not crawl. Article text is stored so you can read it, never republished — an issue carries your blurb and a link.
Keys do one thing
A capture key can capture. It cannot read your inbox and it cannot mail anyone, so leaving one in a script is a bounded decision.
Light and dark, and a phone
Every screen works in both themes and down to 360 pixels, checked automatically against accessibility rules on every change.
Every feature, with its honest status → · Why Curio exists →
Keep the good bits.
Send them Saturday.
Curio does the half of a newsletter that is not sending: capturing, triaging, drafting, assembling, reviewing. Herald owns the subscribers, the opt-in, and the send.
Curio is in active development at Renkara. Nothing here is for sale yet and there is no list to join — write to contact@renkara.com if you want to hear when it opens.
Apple, iPhone, iPad, iOS, iPadOS, Safari, Shortcuts, and Mail are trademarks of Apple Inc. X is a trademark of X Corp. Raycast is a trademark of Raycast Technologies Inc. Alfred is a trademark of Running with Crayons Ltd. Claude and the Model Context Protocol are trademarks of Anthropic, PBC. Curio is not affiliated with, endorsed by, or sponsored by any of them.