First Day Codebase Tour

Paste a file tree and a few key files. Claude gives you the tour a senior engineer would: how a request flows, where things live and what to avoid.

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Output: Text
Added: Sep 18, 2026
Updated: Sep 20, 2026

The prompt

Act as the engineer who has maintained this codebase for three years. I joined the team today.

File tree:
```
[PASTE THE OUTPUT OF: tree -L 3 -I node_modules]
```

The most important files:
[PASTE 2 TO 5 FILES: the entry point, a core model, one typical route or handler]

Give me the tour:
1. One paragraph on what this system does and how it is put together.
2. Follow one typical request from the entry point to the database and back. Name the real files and functions it passes through.
3. The five concepts I have to understand, and how they relate to each other.
4. A table: "I want to change X" on the left, "look in Y" on the right.
5. Things that look wrong but are on purpose. Then things that really are wrong.
6. Three small, safe tasks for my first week that would teach me the most.

If the code I pasted is not enough to answer something, tell me which file you would need. Do not guess.

What it generates

Example

In one paragraph. This is a bookings app for small gyms. A React front end talks to an Express API in /server. Data lives in Postgres and is accessed through Prisma. Anything slow (emails, PDF invoices) goes through a job queue in /jobs so that requests stay fast.

One request, start to finish: a member books a class

web/src/pages/ClassPage.tsx calls POST /api/bookings.
server/routes/bookings.ts validates the body with bookingSchema, then calls canBook(member, class).
server/services/bookings.ts opens a transaction, checks the class is not full, and inserts the row.
It queues a booking-confirmed job and returns 201.
jobs/bookingConfirmed.ts sends the email a few seconds later.

Where things live

I want to change...	Look in
Who is allowed to do what	`server/auth/policies.ts`
An email	`jobs/emails/*.mjml`
The database schema	`prisma/schema.prisma`, then run `migrate dev`
Prices and plans	`server/config/plans.ts` (not the database)

Looks wrong, is on purpose

Every table has deletedAt. Nothing is ever really deleted, so always query through db.active().
Class capacity is checked twice, in the route and inside the transaction. The second check stops two people taking the last spot.

Really is wrong

utils/dates.ts mixes UTC and local time. Do not build on it. There is a ticket.

Your first week

Add the missing index listed in TODO.md. You will learn how migrations work here.
Add the class location to the confirmation email. It touches the whole path above.
Write tests for canBook(). There are edge cases nobody has written down.

I could not see how payments work from these files. Send me server/services/billing.ts and I will add it to the tour.

NoteThis is an example. Results change between runs and model versions. Prompt Podium is a fan project and is not affiliated with Anthropic.

Getting the most from this prompt

When to use it

Your first days in an unfamiliar repository: a new job, an open source project you want to contribute to, or a codebase you inherited. It is also a fast way to write onboarding notes for the next person who joins.

Make it your own

The file tree matters more than you would expect. Keep it to three levels and leave out build output, or the structure gets lost in the noise.
Pick files that show the pattern, not the biggest ones: one entry point, one model, one typical route.
Ask for the request walkthrough again with a different action, for example "now trace a failed login", to see the error paths.

Watch out for

Claude only sees what you paste. Treat the list of things that "really are wrong" as leads to check with a teammate, not as facts. The instruction to name missing files instead of guessing is the most important line in the prompt, so keep it when you adapt it.

How to use this prompt

[01] Copy
Copy the prompt
Use the copy button above. The full text is included, nothing is cut off.
[02] Fill in
Replace the yellow parts
Everything highlighted in yellow is a placeholder. Swap it for your own topic, audience or data.
[03] Vote
Run it in Claude and vote
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Text output

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