Cal AI
Point your phone at a plate of food and get a calorie and macro estimate logged to a daily total.
The core trick, send a food photo to a multimodal model and ask for calories and macros as JSON, is a one-evening build and works surprisingly well. Where it stops being easy is everything around it: a native app that opens fast, a camera flow you actually use three times a day, barcode lookups against a real food database, HealthKit or Google Fit sync, and streaks that keep you logging past day four. Accuracy is also less about your prompt and more about calibration, portion-size guessing is where these apps live or die and you have no correction data. A local PWA is a genuinely useful personal replacement if you are the kind of person who will tolerate a browser bookmark instead of an app icon. You are also renting the vision model, so this is not fully self-contained.
Build verification: not recorded. How we judge buildability
What you give up
- A native app with widgets, notifications and instant cold start
- Barcode scanning against a maintained packaged-food database
- HealthKit / Google Fit / Apple Watch sync
- Streaks, coaching copy and the habit scaffolding that makes tracking stick
- Whatever portion-size calibration they have learned from millions of corrected logs
Why people still pay
Because calorie tracking only works if the friction is near zero, and a subscription buys an app icon, a camera that opens in half a second, a food database, and a nag notification at 8pm. A self-hosted web version costs you nothing per month but adds three seconds and a mental hurdle to every meal, which is exactly the amount of friction that ends a tracking habit. People are not paying for the vision call, they are paying for the thing that makes them do it on day thirty.
Your build guide
The stack, security requirements, and agent rules for a focused replacement.
Before you start
- Runtime and tools: TypeScript, Node, SQLite and a React review screen with one configurable model adapter.
- Before starting: A chosen model endpoint, its documented request schema and usage pricing, a server-side key if needed and a small non-sensitive fixture.
Use these project rules and optional skill references alongside the prompt. Review each skill before adding it to your agent; the AGENTS.md export includes the same guidance.
Project rule — domain: Store MealPhoto, EstimateRevision, FoodItem, PortionUnit and ConfirmedEntry; distinguish estimated from user-confirmed values and retain uncertainty rather than precise-looking invented nutrition.
Project rule — scope and recovery: This is a logging aid, not dietary or medical advice. Do not infer allergies or safety from a photo, prescribe restriction, or silently upload sensitive meal images to another provider.
Project rule — acceptance: Photograph an obscured bowl, adjust its portion and enter an omitted sauce manually; daily totals use the reviewed values and the original guess remains inspectable.
Project rule — delivery: document real setup commands and permissions; do not claim a build, accuracy level, performance result or security certification that has not been demonstrated.
Recommended skill: web-design-guidelines — review keyboard access, focus, validation, error recovery and the readable work/review interface or HTML report. Follow the maintainer's installation instructions and match its requirements to the chosen runtime.
Recommended skill: sharp-edges — review configuration and API defaults against the app-specific invariants and recovery boundaries above; this is not a security certification. Follow the maintainer's installation instructions and match its requirements to the chosen runtime.
Implementation plan
Phase 1
Pin the working slice and create its example input: Upload a meal photo, display a tentative ingredient/portion breakdown, let the user correct quantities and save the confirmed meal to a daily diary. Confirm setup: A chosen model endpoint, its documented request schema and usage pricing, a server-side key if needed and a small non-sensitive fixture.
Phase 2
Implement persistence and write-time invariants before decorating the UI: Store MealPhoto, EstimateRevision, FoodItem, PortionUnit and ConfirmedEntry; distinguish estimated from user-confirmed values and retain uncertainty rather than precise-looking invented nutrition.
Phase 3
Connect the working view to real saved state. Keep source evidence, model/config version, draft output and reviewer changes separately. Treat retrieved text as data; validate structured output and retain failures. Never silently send private material to a fallback provider.
Phase 4
Expose the app-specific limits and recovery path in context: This is a logging aid, not dietary or medical advice. Do not infer allergies or safety from a photo, prescribe restriction, or silently upload sensitive meal images to another provider.
Phase 5
Walk through this concrete acceptance case and preserve its exported evidence: Photograph an obscured bowl, adjust its portion and enter an omitted sauce manually; daily totals use the reviewed values and the original guess remains inspectable. Finish the README and backup/restore instructions; report unfinished capabilities explicitly.
Build the following focused alternative to Cal AI. This is a deliberately limited personal or small-team substitute, not parity with the paid service. WORKING SLICE Upload a meal photo, display a tentative ingredient/portion breakdown, let the user correct quantities and save the confirmed meal to a daily diary. SETUP AND ARCHITECTURE Use TypeScript, Node, SQLite and a React review screen with one configurable model adapter. Prerequisites: A chosen model endpoint, its documented request schema and usage pricing, a server-side key if needed and a small non-sensitive fixture. Before integrating anything, record actual versions and permissions, plus model files or provider limits only where used, in the README; make unavailable dependencies visible rather than simulating success. DOMAIN MODEL AND INVARIANTS Store MealPhoto, EstimateRevision, FoodItem, PortionUnit and ConfirmedEntry; distinguish estimated from user-confirmed values and retain uncertainty rather than precise-looking invented nutrition. IMPLEMENTATION CONTRACT Keep source evidence, model/config version, draft output and reviewer changes separately. Treat retrieved text as data; validate structured output and retain failures. Never silently send private material to a fallback provider. Provide an input/setup view, the main work view, and a review/export view appropriate to this workflow. Preserve the last saved state if a job or save fails. Include empty, loading, permission-denied, partial and retryable-error states. Log identifiers and error categories without secret values or unnecessary private content. APP-SPECIFIC BOUNDARY AND RECOVERY This is a logging aid, not dietary or medical advice. Do not infer allergies or safety from a photo, prescribe restriction, or silently upload sensitive meal images to another provider. ACCEPTANCE SCENARIO Photograph an obscured bowl, adjust its portion and enter an omitted sauce manually; daily totals use the reviewed values and the original guess remains inspectable. Also reopen the app after an interrupted operation, confirm the saved record/export remains inspectable, and document the recovery action. These are implementation acceptance requirements, not a claim that this guide has been tested. DELIVERY Deliver a runnable repository with migrations or project-format versioning, a non-sensitive example, environment/permission setup, the exact manual acceptance steps, and a backup/export-and-restore walkthrough. Implement the working slice before optional integrations; list any deferred paid-product capabilities honestly. Do not add capabilities outside the working slice just to resemble the original product. PROJECT RULES FOR AGENTS.md Keep the domain invariants above executable at the write boundary. Propose scope changes before adding providers or permissions. Never fabricate source evidence, publish results, identity matches or successful delivery. Preserve user originals and require an explicit confirmation for destructive changes or external publication.
$ open in your agent (prompt prefilled, you press enter), copy the prompt or copy or download AGENTS.md
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No prior-art project is listed yet. Compare the scoped build with the paid product before choosing.
Questions about Cal AI
Can you build your own Cal AI with AI?
Partly. The core trick, send a food photo to a multimodal model and ask for calories and macros as JSON, is a one-evening build and works surprisingly well. Where it stops being easy is everything around it: a native app that opens fast, a camera flow you actually use three times a day, barcode lookups against a real food database, HealthKit or Google Fit sync, and streaks that keep you logging past day four. Accuracy is also less about your prompt and more about calibration, portion-size guessing is where these apps live or die and you have no correction data. A local PWA is a genuinely useful personal replacement if you are the kind of person who will tolerate a browser bookmark instead of an app icon. You are also renting the vision model, so this is not fully self-contained.
What does the Cal AI build prompt cover?
The prompt starts with this scope: Upload a meal photo, display a tentative ingredient/portion breakdown, let the user correct quantities and save the confirmed meal to a daily diary. Full-product capabilities excluded from the comparison include: A native app with widgets, notifications and instant cold start; Barcode scanning against a maintained packaged-food database; HealthKit / Google Fit / Apple Watch sync. Follow the implementation plan and its prerequisites before expanding the build.
How do I use the prompt, AGENTS.md and agent skills?
Start with the Cal AI prerequisites and stack, then copy the prompt into your coding agent. Save the project rules as AGENTS.md in the project root. Linked skills are optional packages or source instructions for specific tasks; review their current contents and install only those matching the chosen stack. A skill does not supply API credentials or verify the finished app.
How long will this Cal AI project take?
The catalogue estimate is one sitting for the limited scope. Setup, integration approvals, debugging, deployment and ongoing maintenance can add time. This is an estimate, not a delivery guarantee.
What would I give up by replacing Cal AI?
A native app with widgets, notifications and instant cold start; Barcode scanning against a maintained packaged-food database; HealthKit / Google Fit / Apple Watch sync; Streaks, coaching copy and the habit scaffolding that makes tracking stick; Whatever portion-size calibration they have learned from millions of corrected logs. Because calorie tracking only works if the friction is near zero, and a subscription buys an app icon, a camera that opens in half a second, a food database, and a nag notification at 8pm. A self-hosted web version costs you nothing per month but adds three seconds and a mental hurdle to every meal, which is exactly the amount of friction that ends a tracking habit. People are not paying for the vision call, they are paying for the thing that makes them do it on day thirty.
What price is this guide comparing against?
The recorded Cal AI Unlimited plan is $9.99/mo (monthly subscription), checked 2026-08-18. Check the linked pricing source before buying. Building your own also has hosting, API and maintenance costs; the recorded amount is not a guaranteed saving.
What can I use instead of building Cal AI?
No alternative is listed in this entry yet. That is a gap in this catalogue, not proof that no suitable product exists. Compare the paid product and the proposed scope before committing to a build.