Inline Validation
Tell people what's wrong before they hit submit.
What it adds
Field-level validation that catches problems early without nagging.
What your agent is told to do
4
What your agent is told to do
4-
1
Validate on blur, not on every keystroke — validating while someone is still typing their email is hostile.
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2
Once a field has errored, re-validate as they fix it so the error clears immediately.
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3
Say what is wrong AND how to fix it. 'Invalid' is not an error message.
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4
Keep server-side validation as the source of truth. Client-side validation is a convenience, never a security boundary.
Edge cases it handles
4
Edge cases it handles
4- Submitting must still surface server-side errors the client didn't catch.
- The first errored field must receive focus on a failed submit.
- Async validation (is this username taken?) must be debounced and must not block submit forever.
- Errors must survive a failed submit — never clear the user's input.
Definition of done
8
Definition of done
8- Fields validate on blur, not per keystroke.
- Errors clear as soon as they're fixed.
- Messages explain how to fix the problem.
- Server-side validation still runs and its errors are shown.
- Errors are tied to inputs with aria-describedby and announced.
- A failed submit never discards what the user typed.
- 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
Form Field Shell
Form Field Shell
Wrap every input in one structure so labels, help, and errors behave the same everywhere.
What it does
A single wrapper owning the label, description, error, and status region around any control in the app.
How it works
- 1 Inventory the app's existing fields and find the variations that have accumulated — label above versus beside, error under versus in a tooltip — then route all of them through one shell.
- 2 Generate a stable identifier per field and use it to link the control to its label, its description, and its error, so the association survives re-renders and does not collide when the same field appears twice on a page.
- 3 Support required, optional, read-only, and disabled as declared states of the shell, and let the shell pass them to the control rather than each screen setting them by hand.
Copy the prompt
No account needed
Add this feature to my app:
https://addthisfeature.com/x/form-field-shell
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.