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
uCALL for Umpires
Start playing uCALL for Umpires today - built by and for Major League Umpires
$3.99 · In-app purchases
PRICE
$3.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 3.7
26 ratings · Top 50%
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.
Build your own version
Build Kit
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A product spec, screen plans, and build steps for your coding agent.
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Combine features and design from your favorite apps.
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What should your app do differently? Your note travels with the kit so your coding agent builds around your idea.
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/
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 uCALL for Umpires: map the core Sports 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
Incorporate real-time messaging and push notifications.
Assumption to check: Limited user engagement features like chat or notifications.
Validate with people who use this workflow before building.
Hypothesis 2
Implement a cleaner, more organized layout.
Assumption to check: User interface can feel cluttered.
Validate with people who use this workflow before building.
Hypothesis 3
Optimize app performance for a wider range of devices.
Assumption to check: Inconsistent performance on older devices.
Validate with people who use this workflow before building.
Hypothesis 4
Add comprehensive filtering and sorting capabilities.
Assumption to check: Lack of advanced filtering options for schedules.
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
Start playing uCALL for Umpires today - built by and for Major League Umpires. With over a million pitches to play, you call balls and strikes from the view - or slot - an umpire has behind the plate! Fun for the fan and useful for the training umpire, this immersive simulation lets you call balls and strikes on real Major League pitchers. Need to work on 84mph sliders? Do that in Specific Zone Recognition in uCALL. Need to work on 76mph curveballs low and outside? Do that too in Specific Zone Recognition. Want to see how much the catcher's framing is affecting your calls? Toggle on/off Catcher Framing and see for yourself. After paid download, uCALL for Umpires is completely free to play too! Check out the app preview images and videos to see how fun and easy it is to play uCALL for Umpires. uCALL for Umpires features: • Instant feedback on correct and incorrect calls • Specific Zone Recognition to work outer and inner zones, upper and lower zones • Change Batter Settings to test yourself when a batter crowds the plate • Change Pitch Settings to play against lefty and righty pitchers • Toggle on/off Catcher Framing to see if your calls are affected by the catcher • Change Batter Position to see lefty and righty batters Visit https://decervo.com/contact.html if you need help! Follow us to get news and updates: facebook.com/deCervoProfile Twitter @deCervoProfile https://www.youtube.com/c/deCervoProfile https://decervo.com/ Have fun playing uCALL for Umpires!
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
Zustand
Axios
React Navigation
React Native Paper
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.
