Phone Number Input
Accept phone numbers in the format people know and store them consistently.
What it adds
A phone field with explicit country selection that stores a canonical number while displaying a readable one.
What your agent is told to do
6
What your agent is told to do
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1
Store the canonical international form (E.164) and display the national or international format the user recognises. One stored shape means matching, deduplication, and sending all work.
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2
Make country selection explicit and changeable. Browser locale is not phone country — expatriates, travellers, and anyone with a foreign SIM will be assigned the wrong one.
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Validate per country using real numbering rules, not a single length. Numbers range from about seven to fifteen digits and are not uniform inside one country.
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Capture an extension as a separate field. Appending it to the number breaks dialling and every downstream integration.
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Do not reject a number just because your library does not recognise its prefix. Numbering plans change; warn rather than block, unless the number is being used for delivery.
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6
Caret movement, separator insertion, and paste normalization are owned by Input Masks; extend that rather than writing a second masking implementation.
Edge cases it handles
6
Edge cases it handles
6- A pasted number that already carries a country code must set the country selector, not be treated as a local number.
- Leading zeros in national format must be dropped correctly when converting to E.164 and restored on display.
- Some countries share a calling code (+1, +7); disambiguate by area code rather than guessing.
- Existing stored numbers may not be canonical — migrate them rather than assuming the format on read.
- The mobile keyboard must be a phone keypad, and must permit +, spaces, and dashes.
- A number valid for display may still be undeliverable for SMS; verification, not validation, decides that.
Definition of done
8
Definition of done
8- Numbers are stored in E.164 and displayed in a readable national or international format.
- Country selection is explicit, visible, and independent of locale.
- Valid numbers from at least a dozen countries of differing lengths are accepted.
- Extensions are stored separately from the number.
- Pasting an international number sets the country correctly.
- Unrecognised prefixes warn rather than block.
- The feature matches the existing design system.
- No existing functionality is broken.
Related features
Unit Converter
Unit Converter
Let people convert a value between units without leaving the page they are on.
What it does
An inline converter that takes a typed value in one unit and shows the equivalent in another, in place.
How it works
- 1 Start from the units the app actually deals in. A shipping tool needs weight and length; a recipe tool needs volume and temperature. Ship those and leave the rest out.
- 2 Convert as the user types, with the result visible beside the input rather than behind a submit button. Let either side be edited so the conversion runs in both directions.
- 3 Reuse the app's existing number parsing and display formatting rather than writing new ones. If Locale-Aware Numbers and Dates or Number Formatting Component is already present, the converter must render through it so grouping and decimal marks match the rest of the app.
Copy the prompt
No account needed
Add this feature to my app:
https://addthisfeature.com/x/unit-converter
Voice Dictation
Voice Dictation
Put a microphone in text fields so people can speak their input instead of typing it.
What it does
A dictation control on the app's longer text inputs that transcribes speech into the field as the user talks.
How it works
- 1 Add the control to the fields where typing is genuinely tedious: long descriptions, notes, comments, and message bodies. A microphone on a postcode field is clutter.
- 2 Show interim results in the field as they arrive, visually distinct from committed text, so the speaker can see it is working and correct course before they finish.
- 3 Reuse the app's existing Voice Transcription for the server-side path so one recognition configuration and one set of language settings serve both dictation and recorded audio.
Copy the prompt
No account needed
Add this feature to my app:
https://addthisfeature.com/x/voice-dictation
Code Editor Field
Code Editor Field
Edit code, JSON, and config with syntax highlighting instead of a bare textarea.
What it does
A form field backed by a real code editor: syntax highlighting, a language mode per field, and inline validation that tolerates work in progress.
How it works
- 1 Load the editor library lazily, only on views that use it, and render a usable plain textarea until it arrives. It must never block first paint.
- 2 Set the language mode per field from what the field actually holds, and validate against that mode.
- 3 Report syntax errors as you go, but never block typing or reset the content. Half-written JSON is a normal intermediate state; only submission should be gated.
Copy the prompt
No account needed
Add this feature to my app:
https://addthisfeature.com/x/code-editor-field
How it works
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1
Copy the link
Grab the Markdown instruction URL for this feature.
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2
Give it to your AI
Paste it into Claude Code, Cursor, v0, Lovable — whatever you build with.
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3
It inspects, then implements
Your agent reads your existing app first, then adds the feature to fit it.
Works with your stack
These instructions are written to adapt. They tell the agent to detect your framework, match your existing design system, and reuse what you already have — rather than assuming a particular stack.
Need it tighter than that? Customize the feature and tell it exactly what you're running.