How it works

From one sentence to an app your agent can build

Heidelberg AI PRD interviews you until your idea is a PRD, a product requirements document: what the app does, for whom, what it must not do, and how to check that it works. Then it hands that plan to your coding agent, step by step. Here is every step, as it looks in the app.

Step 1 of 9
Start the way that fits you
- Type your idea in one sentence, or click one of the examples.
- Already have code? Choose its folder or a zip, or paste a public GitHub, GitLab or Codeberg link. The project is read in your browser and fills the PRD.
- Have a PRD from ChatGPT, Gemini or Google Docs? Paste it, or open it with Load in the top bar (.md, .txt, .docx).
Heidelberg AI PRDNew PRDSaved
Load
Turn an app idea into a spec your coding agent can build
Answer a few questions. You get a PRD, AGENTS.md and a kickoff prompt for Claude Code, Codex, OpenCode, Cursor or Hermes.
Already have code? Start from it: Heidelberg AI PRD reads the project in your browser, lists what to fix first and fills the PRD from it.
Choose folderChoose zip
Or paste a public GitHub, GitLab or Codeberg link into the box below, or drop the folder on it.
A sign-up sheet so choir members can claim sheet music before rehearsal.
Enter to send
Your PRD
0 of 18 sections ready
1. Problem, goal & success metricopen
Not covered yet. Answer the questions, or fill it with defaults.
2. Users & rolesopen
Not covered yet. Answer the questions, or fill it with defaults.
3. Core workflowsopen
Not covered yet. Answer the questions, or fill it with defaults.
4. Features & requirementsopen
Not covered yet. Answer the questions, or fill it with defaults.
5. Scope: must / later / neveropen
Not covered yet. Answer the questions, or fill it with defaults.
6. Screens & UIopen
Not covered yet. Answer the questions, or fill it with defaults.
7. Design system & visual styleopen
Not covered yet. Answer the questions, or fill it with defaults.
8. Data modelopen
Not covered yet. Answer the questions, or fill it with defaults.
9. APIs & integrationsopen
Not covered yet. Answer the questions, or fill it with defaults.
10. Auth, permissions & securityopen
Not covered yet. Answer the questions, or fill it with defaults.
11. Performance, privacy & accessibilityopen
Not covered yet. Answer the questions, or fill it with defaults.
12. Edge cases & errorsopen
Not covered yet. Answer the questions, or fill it with defaults.
13. Stack & constraintsopen
Not covered yet. Answer the questions, or fill it with defaults.
14. Existing code & do-not-changeopen
Not covered yet. Answer the questions, or fill it with defaults.
15. Build orderopen
Not covered yet. Answer the questions, or fill it with defaults.
16. Acceptance criteria & testsopen
Not covered yet. Answer the questions, or fill it with defaults.
17. Deployment, environments & secretsopen
Not covered yet. Answer the questions, or fill it with defaults.
18. Open questions & assumptionsopen
Not covered yet. Answer the questions, or fill it with defaults.
Step 2 of 9
Answer the questions
- Every question says why it matters and suggests an answer. Click the ones that fit, then send them, or write your own.
- Attach sketches and screenshots with the clip, or paste them. They go into the pack, linked from the screens they belong to.
- Pick the model under the box: Nemotron is free, Claude Haiku is faster and costs about 1 cent per answer. Watch the PRD on the right fill up.
Heidelberg AI PRDChoir sheet-music sign-upSaved
Load
A sign-up sheet so choir members can claim sheet music before rehearsal.
Nice and small. Three questions to pin it down:
Who signs up: every singer, or only section leaders?Decides whether the app needs roles.Every singer, no roles.Can two singers claim the same piece?Without a rule the agent will guess.One copy per singer, first come first served.Do singers need an account?Sign-in is the most expensive feature to add.No, a name and the choir link are enough.
sketch.jpg
Here is my sketch of the list page.
Enter to send
Your PRD
4 of 18 sections ready
1. Problem, goal & success metric
Singers lose track of who has which piece, so copies go missing before concerts. Success: no missing copies at rehearsal for 4 weeks.
2. Users & roles
About 30 singers claim pieces; one organiser adds pieces and sees who has what.
3. Core workflows
A singer opens the shared link, picks a piece, types their name and claims it.
4. Features & requirements
Must: pieces list, claim, give back, organiser view.
5. Scope: must / later / neveropen
Not covered yet. Answer the questions, or fill it with defaults.
6. Screens & UIopen
Not covered yet. Answer the questions, or fill it with defaults.
7. Design system & visual styleopen
Not covered yet. Answer the questions, or fill it with defaults.
8. Data modelopen
Not covered yet. Answer the questions, or fill it with defaults.
9. APIs & integrationsopen
Not covered yet. Answer the questions, or fill it with defaults.
10. Auth, permissions & securityopen
Not covered yet. Answer the questions, or fill it with defaults.
11. Performance, privacy & accessibilityopen
Not covered yet. Answer the questions, or fill it with defaults.
12. Edge cases & errorsopen
Not covered yet. Answer the questions, or fill it with defaults.
13. Stack & constraintsopen
Not covered yet. Answer the questions, or fill it with defaults.
14. Existing code & do-not-changeopen
Not covered yet. Answer the questions, or fill it with defaults.
15. Build orderopen
Not covered yet. Answer the questions, or fill it with defaults.
16. Acceptance criteria & testsopen
Not covered yet. Answer the questions, or fill it with defaults.
17. Deployment, environments & secretsopen
Not covered yet. Answer the questions, or fill it with defaults.
18. Open questions & assumptionsopen
Not covered yet. Answer the questions, or fill it with defaults.
Step 3 of 9
Watch the PRD get checked
- The bar on the right has one segment per section: a solid segment is ready, orange needs a fix, grey is still open.
- Fixed rules check every answer for vague words, checks nobody can test, missing must-haves and sections that contradict each other.
- An orange section says what is wrong. Answer in the chat, or let the next questions fix it.
Heidelberg AI PRDChoir sheet-music sign-upSaved
Load
1. Every singer, no roles. 2. One copy per singer, first come first served. 3. No, a name and the choir link are enough.
Got it. Two sections on the right are orange now: the login screen clashes with “no sign-in”, and “works well” is not a check anyone can run. Which screens does the organiser need?
Click a question to use its suggestion, or type your answer
Enter to send
Your PRD
11 of 18 sections ready
1. Problem, goal & success metric
Singers lose track of who has which piece, so copies go missing before concerts. Success: no missing copies at rehearsal for 4 weeks.
2. Users & roles
About 30 singers claim pieces; one organiser adds pieces and sees who has what.
3. Core workflows
A singer opens the shared link, picks a piece, types their name and claims it.
4. Features & requirements
Must: pieces list, claim, give back, organiser view.
5. Scope: must / later / never
Must: list, claim, organiser view · Later: email reminders · Never: payments, accounts.
6. Screens & UI
Pieces list, claim dialog, organiser table (images/sketch.jpg).
7. Design system & visual style
Calm and readable: one accent color, large tap targets, works on phones.
8. Data model
Piece (title, composer, copies) · Claim (piece, singer name, date).
9. APIs & integrationsopen
Not covered yet. Answer the questions, or fill it with defaults.
10. Auth, permissions & security1 fix
Auth says no sign-in, but Screens has a login page.
No sign-in: anyone with the choir link can claim.
11. Performance, privacy & accessibilityopen
Not covered yet. Answer the questions, or fill it with defaults.
12. Edge cases & errorsopen
Not covered yet. Answer the questions, or fill it with defaults.
13. Stack & constraints
Next.js and SQLite on one free host.
14. Existing code & do-not-change
New project, no existing code.
15. Build order
Slice 1: pieces list · Slice 2: claim a piece · Slice 3: organiser view.
16. Acceptance criteria & tests1 fix
“Works well” can’t be tested. Say what the user does and sees.
The app works well on phones.
17. Deployment, environments & secretsopen
Not covered yet. Answer the questions, or fill it with defaults.
18. Open questions & assumptionsopen
Not covered yet. Answer the questions, or fill it with defaults.
Step 4 of 9
Steer the interview
- Ask now on a section makes the next questions about it.
- Later parks a section until the rest is done; Back in brings it back. It is still needed for a complete PRD.
- Tired of questions? The button under the last answer fills the empty sections with sensible defaults, or fixes the flagged ones.
Heidelberg AI PRDChoir sheet-music sign-upSaved
Load
Ask me about Design system & visual style next.
Let’s settle the look:
1Which feeling should the app have?Gives the agent one style to follow on every screen.Calm and readable, one accent color, large tap targets.
Click a question to use its suggestion, or type your answer
Enter to send
Your PRD
15 of 18 sections ready
1. Problem, goal & success metric
Singers lose track of who has which piece, so copies go missing before concerts. Success: no missing copies at rehearsal for 4 weeks.
2. Users & roles
About 30 singers claim pieces; one organiser adds pieces and sees who has what.
3. Core workflows
A singer opens the shared link, picks a piece, types their name and claims it.
4. Features & requirements
Must: pieces list, claim, give back, organiser view.
5. Scope: must / later / never
Must: list, claim, organiser view · Later: email reminders · Never: payments, accounts.
6. Screens & UI
Pieces list, claim dialog, organiser table (images/sketch.jpg).
7. Design system & visual styleopen
Not covered yet. Answer the questions, or fill it with defaults.
8. Data model
Piece (title, composer, copies) · Claim (piece, singer name, date).
9. APIs & integrationslater
Not covered yet. Answer the questions, or fill it with defaults.
10. Auth, permissions & security
No sign-in: anyone with the choir link can claim.
11. Performance, privacy & accessibility
Loads in under 2 s on a phone; names are visible to the choir only.
12. Edge cases & errors
A piece with no copies left shows “All taken”.
13. Stack & constraints
Next.js and SQLite on one free host.
14. Existing code & do-not-change
New project, no existing code.
15. Build order
Slice 1: pieces list · Slice 2: claim a piece · Slice 3: organiser view.
16. Acceptance criteria & tests
Slice 2: claim a piece → the piece shows your name. Run tests with: npm test
17. Deployment, environments & secretsopen
Not covered yet. Answer the questions, or fill it with defaults.
18. Open questions & assumptions
None open.
Step 5 of 9
Find data your app can use
- Open APIs & integrations on the right and click Find data sources.
- It searches the web for open data and APIs that fit your app and adds them as a table, with their limits and terms. Three searches per session.
Heidelberg AI PRDChoir sheet-music sign-upSaved
Load
Only Deployment is still open. Want data the app could pull in? Try Find data sources in APIs & integrations.
Click a question to use its suggestion, or type your answer
Enter to send
Your PRD
17 of 18 sections ready
1. Problem, goal & success metric
Singers lose track of who has which piece, so copies go missing before concerts. Success: no missing copies at rehearsal for 4 weeks.
2. Users & roles
About 30 singers claim pieces; one organiser adds pieces and sees who has what.
3. Core workflows
A singer opens the shared link, picks a piece, types their name and claims it.
4. Features & requirements
Must: pieces list, claim, give back, organiser view.
5. Scope: must / later / never
Must: list, claim, organiser view · Later: email reminders · Never: payments, accounts.
6. Screens & UI
Pieces list, claim dialog, organiser table (images/sketch.jpg).
7. Design system & visual style
Calm and readable: one accent color, large tap targets, works on phones.
8. Data model
Piece (title, composer, copies) · Claim (piece, singer name, date).
9. APIs & integrations
Source What Limits
IMSLP Public-domain scores Free, no key
MusicBrainz API Works and composers Free, 1 request/s
Searches the web for APIs and open data this app could use, with their limits and terms. Claude Haiku 5.5, about 1 ct per search, 3 per session.
Added 2 sources to the table above. 2 of 3 searches left in this session.
10. Auth, permissions & security
No sign-in: anyone with the choir link can claim.
11. Performance, privacy & accessibility
Loads in under 2 s on a phone; names are visible to the choir only.
12. Edge cases & errors
A piece with no copies left shows “All taken”.
13. Stack & constraints
Next.js and SQLite on one free host.
14. Existing code & do-not-change
New project, no existing code.
15. Build order
Slice 1: pieces list · Slice 2: claim a piece · Slice 3: organiser view.
16. Acceptance criteria & tests
Slice 2: claim a piece → the piece shows your name. Run tests with: npm test
17. Deployment, environments & secretsopen
Not covered yet. Answer the questions, or fill it with defaults.
18. Open questions & assumptions
None open.
Step 6 of 9
Download the pack and start your agent
- When every section is ready, click Download pack in the top bar. You get one zip: PRD.md, AGENTS.md, CLAUDE.md, STEPS.md, PROGRESS.md, DESIGN.md, DEPLOY.md and your images.
- Unzip it into an empty folder, open Claude Code, Codex, OpenCode, Cursor or Hermes there, and paste the first prompt from KICKOFF.md.
- The agent builds one slice at a time and ticks it off when its checks pass. Small or free model? Take the compact pack.
Heidelberg AI PRDChoir sheet-music sign-upSaved
Load
Pack downloaded. Now start your agent
1. Unzip prd-pack.zip into a new, empty folder.
2. Open your coding agent in that folder: Claude Code, Codex, OpenCode, Cursor or Hermes.
3. Paste the first prompt from KICKOFF.md. The agent then works through the build order by itself.
This pack is linked to this PRD. Keep this page open: after every step the agent reports here and Claude Haiku proposes PRD fixes.
Your agent runs on a small or free model that says the files are too large? Download the compact pack: one card per step instead of the whole PRD.
Deployment is set: Vercel free tier, no secrets.
The PRD is complete. Download the pack, or keep refining.
Click a question to use its suggestion, or type your answer
Enter to send
Your PRD
18 of 18 sections ready
1. Problem, goal & success metric
Singers lose track of who has which piece, so copies go missing before concerts. Success: no missing copies at rehearsal for 4 weeks.
2. Users & roles
About 30 singers claim pieces; one organiser adds pieces and sees who has what.
3. Core workflows
A singer opens the shared link, picks a piece, types their name and claims it.
4. Features & requirements
Must: pieces list, claim, give back, organiser view.
5. Scope: must / later / never
Must: list, claim, organiser view · Later: email reminders · Never: payments, accounts.
6. Screens & UI
Pieces list, claim dialog, organiser table (images/sketch.jpg).
7. Design system & visual style
Calm and readable: one accent color, large tap targets, works on phones.
8. Data model
Piece (title, composer, copies) · Claim (piece, singer name, date).
9. APIs & integrations
None needed for version 1.
10. Auth, permissions & security
No sign-in: anyone with the choir link can claim.
11. Performance, privacy & accessibility
Loads in under 2 s on a phone; names are visible to the choir only.
12. Edge cases & errors
A piece with no copies left shows “All taken”.
13. Stack & constraints
Next.js and SQLite on one free host.
14. Existing code & do-not-change
New project, no existing code.
15. Build order
Slice 1: pieces list · Slice 2: claim a piece · Slice 3: organiser view.
16. Acceptance criteria & tests
Slice 2: claim a piece → the piece shows your name. Run tests with: npm test
17. Deployment, environments & secrets
Vercel free tier, one environment, no secrets.
18. Open questions & assumptions
None open.
Step 7 of 9
Fix the PRD while the agent builds
- Keep the page open. After every step your agent reports back into the chat.
- When it hits a gap, you get a proposed fix. Apply it and the agent reads the updated PRD before its next step, or Discard it and say what to do instead.
Heidelberg AI PRDChoir sheet-music sign-upSaved
Load
From your coding agentSlice 2 done: claim a piece. Open question: what happens when two singers claim the last copy at the same time?
Good catch. Here is a rule for it:
Proposed PRD changes (1) · your agent sees them only after you apply them
Edge cases & errors
The first claim saved wins; the second singer sees “Just taken, pick another piece”.
Or write below what to change instead.
Click a question to use its suggestion, or type your answer
Enter to send
Your PRD
18 of 18 sections ready
1. Problem, goal & success metric
Singers lose track of who has which piece, so copies go missing before concerts. Success: no missing copies at rehearsal for 4 weeks.
2. Users & roles
About 30 singers claim pieces; one organiser adds pieces and sees who has what.
3. Core workflows
A singer opens the shared link, picks a piece, types their name and claims it.
4. Features & requirements
Must: pieces list, claim, give back, organiser view.
5. Scope: must / later / never
Must: list, claim, organiser view · Later: email reminders · Never: payments, accounts.
6. Screens & UI
Pieces list, claim dialog, organiser table (images/sketch.jpg).
7. Design system & visual style
Calm and readable: one accent color, large tap targets, works on phones.
8. Data model
Piece (title, composer, copies) · Claim (piece, singer name, date).
9. APIs & integrations
None needed for version 1.
10. Auth, permissions & security
No sign-in: anyone with the choir link can claim.
11. Performance, privacy & accessibility
Loads in under 2 s on a phone; names are visible to the choir only.
12. Edge cases & errors
The first claim saved wins; the second singer sees “Just taken, pick another piece”.
13. Stack & constraints
Next.js and SQLite on one free host.
14. Existing code & do-not-change
New project, no existing code.
15. Build order
Slice 1: pieces list · Slice 2: claim a piece · Slice 3: organiser view.
16. Acceptance criteria & tests
Slice 2: claim a piece → the piece shows your name. Run tests with: npm test
17. Deployment, environments & secrets
Vercel free tier, one environment, no secrets.
18. Open questions & assumptions
None open.
Step 8 of 9
Share it, or show it in the gallery
- Share in the top bar gives you a private link to continue on another device, and a read-only link for others.
- Add it to the example gallery with your name, a picture and what you learned. Only the PRD is public, never the chat.
Heidelberg AI PRDChoir sheet-music sign-upSaved
Load
Share
Continue later · private, anyone with it can edit
Share the result · read-only PRD and download, no chat
Example gallery · public, the PRD only, never the chat
Your name on the tile · optionalThis PRD has no names, emails or private details. Anyone can read and download it; the chat stays private.
Slice 3 done: organiser view. All checks pass.
Click a question to use its suggestion, or type your answer
Enter to send
Your PRD
18 of 18 sections ready
1. Problem, goal & success metric
Singers lose track of who has which piece, so copies go missing before concerts. Success: no missing copies at rehearsal for 4 weeks.
2. Users & roles
About 30 singers claim pieces; one organiser adds pieces and sees who has what.
3. Core workflows
A singer opens the shared link, picks a piece, types their name and claims it.
4. Features & requirements
Must: pieces list, claim, give back, organiser view.
5. Scope: must / later / never
Must: list, claim, organiser view · Later: email reminders · Never: payments, accounts.
6. Screens & UI
Pieces list, claim dialog, organiser table (images/sketch.jpg).
7. Design system & visual style
Calm and readable: one accent color, large tap targets, works on phones.
8. Data model
Piece (title, composer, copies) · Claim (piece, singer name, date).
9. APIs & integrations
None needed for version 1.
10. Auth, permissions & security
No sign-in: anyone with the choir link can claim.
11. Performance, privacy & accessibility
Loads in under 2 s on a phone; names are visible to the choir only.
12. Edge cases & errors
A piece with no copies left shows “All taken”.
13. Stack & constraints
Next.js and SQLite on one free host.
14. Existing code & do-not-change
New project, no existing code.
15. Build order
Slice 1: pieces list · Slice 2: claim a piece · Slice 3: organiser view.
16. Acceptance criteria & tests
Slice 2: claim a piece → the piece shows your name. Run tests with: npm test
17. Deployment, environments & secrets
Vercel free tier, one environment, no secrets.
18. Open questions & assumptions
None open.
Step 9 of 9
Plan the next version
- Built version 1? Next version in the top bar moves its must-haves into “Existing code”, so the agent does not build them again.
- Pick items from your Later list or add new ones; you get new build steps and checks. Came back after a build that went wrong? Load the pack and say what the agent got wrong.
Heidelberg AI PRDChoir sheet-music sign-upSaved
Load
Start version 2
Built version 1? Its must-haves move to “Existing code”, so your agent knows they are there and doesn’t build them again. Pick what comes next; then I write the new build steps and checks.
From your Later listEmail reminders before rehearsal
Something new · one per lineOrganiser can add new pieces
Version 1 is built and live.
Click a question to use its suggestion, or type your answer
Enter to send
Your PRD
18 of 18 sections ready
1. Problem, goal & success metric
Singers lose track of who has which piece, so copies go missing before concerts. Success: no missing copies at rehearsal for 4 weeks.
2. Users & roles
About 30 singers claim pieces; one organiser adds pieces and sees who has what.
3. Core workflows
A singer opens the shared link, picks a piece, types their name and claims it.
4. Features & requirements
Must: pieces list, claim, give back, organiser view.
5. Scope: must / later / never
Must: list, claim, organiser view · Later: email reminders · Never: payments, accounts.
6. Screens & UI
Pieces list, claim dialog, organiser table (images/sketch.jpg).
7. Design system & visual style
Calm and readable: one accent color, large tap targets, works on phones.
8. Data model
Piece (title, composer, copies) · Claim (piece, singer name, date).
9. APIs & integrations
None needed for version 1.
10. Auth, permissions & security
No sign-in: anyone with the choir link can claim.
11. Performance, privacy & accessibility
Loads in under 2 s on a phone; names are visible to the choir only.
12. Edge cases & errors
A piece with no copies left shows “All taken”.
13. Stack & constraints
Next.js and SQLite on one free host.
14. Existing code & do-not-change
New project, no existing code.
15. Build order
Slice 1: pieces list · Slice 2: claim a piece · Slice 3: organiser view.
16. Acceptance criteria & tests
Slice 2: claim a piece → the piece shows your name. Run tests with: npm test
17. Deployment, environments & secrets
Vercel free tier, one environment, no secrets.
18. Open questions & assumptions
None open.

Develop a structured product requirements document before starting an app, instead of vibe-coding frustration

Start now

Source	What	Limits
IMSLP	Public-domain scores	Free, no key
MusicBrainz API	Works and composers	Free, 1 request/s

Start the way that fits you

Turn an app idea into a spec your coding agent can build

Answer the questions

Watch the PRD get checked

Steer the interview

Find data your app can use

Download the pack and start your agent

Fix the PRD while the agent builds

Share it, or show it in the gallery

Plan the next version

Develop a structured product requirements document before starting an app, instead of vibe-coding frustration