Features
The Half of a Newsletter That Isn't Sending
Links pile up all week. On Saturday morning, something good goes out. Curio does the collecting, the triage, the drafting and the assembly, then hands the finished issue to Herald — which owns the subscribers and the send. The marketing site is live at curio.renkara.com; the application is in development, and the notes below say which parts are running and which are not.
Capture
Eight Ways In, One Inbox
You Never Open the App to Save Something
Eight capture paths, five of them running today: a bookmarklet, a designated Chirp channel, an assistant over MCP, watched RSS and Atom feeds, and a revocable key for Shortcuts, Raycast, Alfred or curl. A share sheet, a private forwarding address and a browser extension are designed and not yet built.
Bookmarklet
One click from any page in any browser. Opens a small window, offers a note, closes itself. Deliberately not the full app — saving a link should be instant.
Capture From a Chat Message
Post a link in a designated Chirp channel and it is captured, with the sentence you wrote around it kept as the note. The note is the highest-value field in the system, so the path that captures it for free matters.
Capture by Assistant, Over MCP
Claude, or any Model Context Protocol client, can save links on your behalf with the reason attached. The reason is what makes a later draft worth reading.
Watched Feeds in Their Own Lane
Follow an RSS or Atom feed and new entries arrive as suggestions, never entering the inbox until you say so. The inbox keeps meaning “things I chose,” which is what keeps triage fast.
Deduplication on Arrival
The same article from a feed, a chat message and a bookmarklet is one item with three arrivals recorded. Tracking parameters are stripped per host, shorteners are followed, and two URLs telling the same story are offered as a suggested merge — never merged for you.
Read
Every Link Arrives Legible
The Save Never Waits on the Fetch
Title, author, publication, date, standfirst, hero image, language and reading time are pulled in the background. Capture returns immediately; the metadata catches up.
Reader View
The article's text stripped of navigation and subscribe-nags, so a piece can be judged without leaving Curio or spending a second paywall view on it.
Posts and Videos Read Properly
X, YouTube, Vimeo, Bluesky and Mastodon are read through their own metadata rather than scraped, because their pages are shells that scrape into nothing.
A Paywall Doesn't Lose the Link
When a page cannot be read, the item survives with its URL, your note, and a plain explanation of what happened. It stays perfectly usable — you usually know exactly what it was.
Triage
A Hundred Items Without Touching the Mouse
Keyboard-Complete
j and k to move, 1–9 to file into a publication, x to drop, u to undo, o to open. Every destructive action is undoable, and no shortcut fires while you are typing a note.
Your Note Outranks the Site's Blurb
One sentence on why you kept something is worth more than the article's own marketing copy, so Curio shows it first and never overwrites it.
One Link, Several Newsletters
The blurb belongs to the issue, not to the link, so the same article can run in two publications and read completely differently in each. Most tools in this category cannot express that at all.
Search Everything, Including What You've Sent
Titles, standfirsts, notes, URLs and tags, sent issues included — so “have I used this before?” has an answer instead of a guess.
Compose
Several Newsletters, Each With Its Own Voice
Publications
Each is one newsletter with its own sections, schedule, template, voice and mailing list. Pause one without touching capture.
Sections You Define
Named buckets — “Long reads,” “Tools,” “One more thing” — with optional guidance the writing follows and an optional cap so one section cannot swallow an issue.
Issues Assemble Themselves
Everything filed since the last issue, ordered by section, with a draft blurb waiting on each. Assembling twice never produces two issues, and an empty week produces none at all rather than an empty newsletter.
Review on a Phone
Reorder, edit any blurb, write the intro, drop something back to next week's queue. The Saturday morning screen works at 360 pixels, because that is where the pass actually happens.
Draft
A First Pass in Your Voice, Never the Last Word
Written From Why You Kept It
The capture note carries more weight in the prompt than the article does. A model handed “the third chart is the whole argument” writes something no summarizer would, because a summary is about the article and a blurb is about why you are sending it.
Voice Profiles, Versioned
Describe your tone in your own words and give examples of blurbs you consider correct. Versioned, so changing the profile never rewrites what is already drafted. Five starter voices are in progress.
Re-Draft With a Nudge
“Shorter.” “Less arch.” “Lead with the number.” A draft you have edited is never overwritten by a later one.
You Can See How Much Is Yours
Every blurb is marked drafted, drafted-then-edited, or written by you. The proportion is shown on the issue because it is the only honest measure of whether the drafting is earning its keep.
What It Cost
Token spend per issue, on the issue. A newsletter that costs more to draft than it earns in attention should be legible as such. Grounded drafting — saying nothing rather than inventing something confident about a two-line stub — is in progress.
Publish
Deliberate, and Impossible to Send Twice
The Preview Is the Email
Rendered by the same engine the send uses, so what is approved is exactly what arrives. Curio emits Markdown; Herald turns it into email-safe HTML with its own renderer.
Pick the List, Don't Retype It
Choose from the Herald mailing lists you own. A list you do not own cannot appear, because Herald decides that, not Curio.
A Confirmation That Names the List
Not “are you sure?” — the thing worth checking before an unrecallable action is where it is going, so the dialog says it, and the send is refused if the list changed while it was being read.
A Crash Cannot Produce a Duplicate Send
Curio records the created Herald draft before it asks for the send, so a retry resumes rather than repeats. The one failure in this product that could not be undone is the one it is built hardest against.
Templates, Versioned Per Publication
Editable per publication and versioned, so an archived issue always shows what actually went out. A classic layout and a stripped-back one ship today; digest, magazine and link-only editions are in progress.
Measure
Which Links Did People Actually Read?
The Full Archive
Every issue kept as sent — its items, its blurbs, the template version it used — searchable alongside everything ever saved.
Opens and Clicks, Pulled Back From Herald
Fetched automatically, more often just after a send and rarely once the numbers settle. Per-link click ranking, carried back to the item so next week's triage knows, is in progress.
“Already Sent This?”
Capturing something published before says so on the spot, with the issue and the date.
Agents and the Line
An Assistant Can Take an Issue Right Up to the Send
32 MCP Tools, None of Which Can Send
Capture, triage, publications, feeds, issue assembly, blurb drafting and preview are all exposed over the Model Context Protocol. 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.
Curio Never Holds a Subscriber
It stores the id of a Herald mailing list and nothing else about the people on it. Opt-in, unsubscribes, bounces and deliverability live in Herald, in one place rather than two.
Capture Keys Do Exactly One Thing
A capture key can capture. It cannot read the inbox and it cannot mail anyone, so leaving one in a shell script or an iOS Shortcut is a bounded decision rather than an open door.
Accessibility
Built for Everyone
WCAG 2.1 AA Compliance
4.5:1 contrast for body text, 3:1 for large text and UI components, in both light and dark themes.
Keyboard Navigation
Every interaction reachable via keyboard. Logical tab order, visible focus indicators, Escape-to-dismiss for modals.
Screen Reader Support
VoiceOver, NVDA, and JAWS tested. Semantic HTML, ARIA labels, live regions for dynamic updates.
Reduced Motion
Respects
prefers-reduced-motion. Usable at 200% zoom. Touch targets meet 44x44 minimum.
How It Works
From Forty Open Tabs to Six Good Paragraphs
Step 1: Capture
Eight paths in, one inbox, deduplicated on arrival. Tracking parameters stripped, shorteners followed, near-duplicates offered as a merge rather than merged for you.
Step 2: Triage
Keyboard-complete, undoable, and built for the week where sixty items have to become six. Your note leads; the site's own blurb never overwrites it.
Step 3: Draft
A first pass written from why you kept it, in a voice profile you wrote, marked as drafted so the proportion you rewrote stays visible on the issue.
Step 4: Hand to Herald
The preview is the email. The confirmation names the list. Curio records the draft before asking for the send, then Herald sends it — or schedules it. Never automatically.
Technical Specifications
Under the Hood
Backend
- FastAPI (Python 3.12+)
- PostgreSQL database
- Background metadata and article fetch
- Per-host tracking-parameter stripping
- Herald API integration for lists, drafts and metrics
- MCP server (32 tools, none able to send)
Frontend
- React 19
- Keyboard-complete triage with universal undo
- Reader view and issue review
- Works down to 360 pixels
- Light and dark mode
Capture Surfaces
- Bookmarklet — any browser, any machine
- Chirp channel — the note comes free
- MCP — Claude or any client
- Watched RSS and Atom feeds
- Revocable capture keys for Shortcuts, Raycast, Alfred, curl
- Share sheet, email forwarding and a browser extension: designed, not built
The Boundary
- Curio owns what goes in the issue
- Herald owns who receives it
- No subscriber record ever leaves Herald
- Curio emits Markdown; Herald renders the email
- Assembly is automated; sending never is
- Marketing site live at curio.renkara.com; the application is in development
Development
100% Built by Claude
Every tool in the Renkara fleet was built by Claude (Anthropic) working alongside a single human supervisor. Every line of code, every test, every deployment: AI-authored with human direction. The leverage factor across the fleet runs in the 20x–50x range, with individual sessions regularly exceeding 100x.
See the daily leverage records for per-task numbers across the full build history.