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
eFax® Plus-Pro-Protect
Transform your iPhone into a portable mobile fax machine with the eFax® app
Free · In-app purchases
PRICE
Free
In-app purchases
BUSINESS MODEL
Freemium
No overall Grossing estimate available
RATING
★ 4.7
29,048 ratings · Top 15%
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 included18 files
A product spec, phased build plan, differentiation notes, and screen references.
- START_HERE
- AGENTS
- EVIDENCE
- SPEC
- BUILD_PLAN
- DIFFERENTIATION
- skills/
- screens/
Preview a sample Build Kit No email needed
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 eFax® Plus-Pro-Protect: map the core Business workflow, choose the smallest differentiated feature set, define the data and monetization boundaries, then prototype the riskiest user journey first.
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App evidence
Original App Store material. Ratings and screenshots describe the existing app, not proof of demand for your version.
Screenshots
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App Store description
Transform your iPhone into a portable mobile fax machine with the eFax® app. - Designed specifically for our eFax® Plus, eFax®Pro and eFax®Protect subscribers - Enjoy mobile faxing wherever you are without the need for a fax machine - Send and receive faxes directly from your iPhone or iPad. - Secure and reliable faxing ensures your documents are transmitted safely. - Hassle-free online fax service with a user-friendly interface - No set-up fees or long-term commitment FAQs Q. Can I send a fax from my iPhone? A. Yes, you can receive and send a fax from your iPhone using the eFax® app. Simply download the app, register your account, and start faxing. Q. What is eFax® A. eFax® is the official digital, cloud-based fax brand service, that enables you to fax online without requiring a physical fax machine, supplies or dedicated phone line. Q. Does eFax® offer other online faxing options beside the mobile app? A. Yes. eFax subscribers can also send and receive faxes from the eFax web portal and even fax by email with no fax machine required. Q. Is there a free fax app for iPhone? A. The eFax® mobile app is included at no extra cost with an eFax® subscription. New users can download the app and sign up through iTunes (USA only) or the eFax® website. Q. Why choose eFax® A. eFax® is the official online fax brand and a global online fax leader serving 25M+ users since 1995 eFax® subscription details: The $16.99 (USD) monthly subscription fee includes a personal fax number and 300 fax pages per month. The fee will be charged through iTunes when you confirm your purchase in the app. You can manage your subscription in your iTunes account. Your monthly subscription will renew automatically unless your subscription is canceled in your iTunes account by turning off auto-renew 24-hours before the end of the current period. Your account will be charged $16.99 for renewal within 24-hours prior to the end of the current period. No cancellation of the current month allowed during the active subscription period. For further terms and conditions see https://www.efax.com/legal#agreement. Download the eFax® faxing app and start faxing in minutes
Written user reviews are not shown here. Check current App Store reviews >
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
Offer more free credits per month to attract users.
Assumption to check: Limited free tier usage for sending faxes
Validate with people who use this workflow before building.
Hypothesis 2
Increase document size limit for uploads.
Assumption to check: Document upload size limits
Validate with people who use this workflow before building.
Hypothesis 3
Simplify the subscription management process.
Assumption to check: Complicated subscription management
Validate with people who use this workflow before building.
Hypothesis 4
Implement a live chat feature for faster support.
Assumption to check: Inconsistent user support response times
Validate with people who use this workflow before building.
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 Navigation
Expo Document Picker
AsyncStorage
Axios
React Hook Form
BUILD KIT DIFFICULTY
Advanced
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.
