Feature spec
Goal: Send a clear invoice after finishing a job.
- Add a client, line items, a due date, and payment instructions.
- Preview the total before exporting a PDF.
- Keep an editable draft if export fails.
App Overview
Spool for Safari
Spool is a Safari extension that adds a few features to the Threads web app.
$1.99 · In-app purchases
PRICE
$1.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
N/A
No ratings yet
Evidence scope: No current overall US chart position is available. Category-chart positions shown in discovery are a separate scope. Revenue is a directional model estimate, not verified earnings.
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Build Kit
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A product spec, screen plans, and build steps for your coding agent.
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What's included15 files
A product spec, phased build plan, differentiation notes, and screen references.
- START_HERE
- AGENTS
- EVIDENCE
- SPEC
- BUILD_PLAN
- DIFFERENTIATION
- skills/
- screens/
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Illustrative example: an invoice app for independent contractors. Your kit is tailored to the app you choose; this is not its generated content.
Screen plan
Invoice editor: Client at the top, editable line items in the middle, total and preview action at the bottom.
States: Empty draft, validation errors beside each field, exporting, and a retry action that preserves the draft.
Differentiate and validate
Hypothesis: Contractors need faster repeat invoices more than more templates.
First experiment: Test duplicating a previous job with five contractors. Watch where they hesitate before expanding the feature set.
The full kit adds a phased build plan, evidence notes, tool prompts, and implementation guidance. It is a plan for your coding agent, not a finished app.
Usage: Mechanics are fair game; never reuse the original name, branding, assets, or verbatim copy.
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Free quick prompt For a smaller starting point
Quick prompt
Good fit for mobile-first iOS and Android prototypes with managed app scaffolding.
// RORK SYSTEM PROMPT
Rork plan preview for Spool for Safari: map the core Social Networking workflow, choose the smallest differentiated feature set, define the data and monetization boundaries, then prototype the riskiest user journey first.
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Opportunities
AI-GENERATED OPPORTUNITY HYPOTHESES
These are generated suggestions, not verified review quotations. Check current App Store reviews and speak with users before treating a possible gap as a requirement.
Hypothesis 1
Implement a direct messaging feature to increase user interaction.
Assumption to check: Low engagement due to lack of features like direct messaging.
Validate with people who use this workflow before building.
Hypothesis 2
Add content reporting and moderation features.
Assumption to check: Limited content moderation tools.
Validate with people who use this workflow before building.
Hypothesis 3
Incorporate a search and explore feature for trending posts.
Assumption to check: Difficult to discover new content.
Validate with people who use this workflow before building.
Hypothesis 4
Clearly define benefits of in-app purchases for better user understanding.
Assumption to check: In-app purchases are unclear.
Validate with people who use this workflow before building.
App evidence
Original App Store material. Ratings and screenshots describe the existing app, not proof of demand for your version.
App Store description
Spool is a Safari extension that adds a few features to the Threads web app. With Spool, you can set “Following” as your default timeline. You can also filter posts from certain users (e.g. engagement farmers) or based on keywords (e.g. engagement bait). Threads like to show me posts from complete strangers, but I think it's rude to mute them. So, instead of hiding posts completely, I added a reveal button to show filtered posts. (Filters are saved in iCloud, so sometimes you have to quit and reopen Safari for the new filters to take effect.) Spool also removes the l.threads.net redirect tracking when you click on an external link. Since Safari extensions don’t work on web apps added to your iPhone or iPad home screen, the mobile version of Spool lets you turn the app into a simple Threads browser, with your settings intact. If you use Threads but don’t like their approach to maximizing engagement, give Spool a try. I hope you find it useful.
Written user reviews are not shown here. Check current App Store reviews >
Screenshots
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Build scope
Plan a focused first version with your coding agent. These are planning assumptions, not a delivery guarantee.
Define the first version
Choose one audience and one core workflow. Use the kit to agree on its screens, data, and acceptance criteria before building.
Set boundaries
Decide which secondary features, integrations, and platform support can wait. Your version does not need to reproduce everything in the original.
Check the hard parts
Validate external services, specialist technology, data access, and ongoing costs for your chosen scope.
SUGGESTED BUILD STACK
React Native
Expo
FastAPI
Zustand
React Navigation
Axios
BUILD KIT DIFFICULTY
Intermediate
From the Build Kit assessment.
A reliable timeline needs an agreed scope and a technical check. Ask your agent to estimate the phases in BUILD_PLAN.md after that review.
