Your first session: ask a real table a question

On the previous page you read the log of a session that had already run; now it's your turn to run it on your own computer. You'll ask Claude Code to download NASA's exoplanet catalog from the internet and work out what percentage of confirmed planets were discovered by the transit method.

This table has two advantages for a first run. First, it's public, so you practice without exposing private files or passwords from work. Second, it has more than 40,000 rows (40,350 on October 31, 2026), a size that already calls for code instead of counting by eye.

How Claude Code reaches your data

In a regular chat, you upload a file by hand in the browser. An agent installed on your computer reaches data through the tools its harness gives it:

• Local files: it reads the files already in your working directory and saves new files right there, like the CSV file you'll download today.
• Commands: it uses the terminal to pull data from an address on the internet, look at a file's first lines or run a Python script that does the math.
• Connectors and credentials: at work it can also query databases or internal systems through connectors and your access credentials. In your first session we leave passwords and internal systems out: you work only with a dedicated folder and a publicly available address.

That's why the folder you open the session from matters. If you open Claude Code inside your exoplanetas folder, that's its working directory and that's where it saves planetas.csv. If you open it from Downloads or your desktop, it scatters the files over there instead.

Start your session in the exoplanetas folder

Open Claude Code inside your exoplanetas folder, just as you set it up in Module 1. If you use the desktop app, check that the permission mode is Manual; if you use the terminal, stay in the normal mode where it asks before each action. For this practice, avoid any mode that approves steps automatically.

Copy this whole request, paste it into Claude Code and press Enter:

Read before you approve

After you send your request, Claude Code pauses before answering and shows you a permission prompt. That prompt is your checkpoint: it shows which tool it wants to use and with exactly what instructions.

In the test session we ran on October 31, 2026 with Claude Code 2.1.314 in an empty folder, the first thing it asked to approve was this three-part command:

curl -sS -o planetas.csv "https://exoplanetarchive.ipac.caltech.edu/TAP/sync?query=select+pl_name,hostname,disc_year,discoverymethod,default_flag+from+ps&format=csv"; ls -l planetas.csv; head -3 planetas.csv

Even if you don't write terminal commands, you can read what each part does before you give permission:

• curl -sS -o planetas.csv "https://exoplanetarchive..." connects to the NASA address you gave it and saves the result in the file planetas.csv in your current folder.
• ls -l planetas.csv checks that the file was created and shows its size (1,816,982 bytes in the test session).
• head -3 planetas.csv shows the file's first three lines so you can see the column names (pl_name,hostname,disc_year,discoverymethod,default_flag).

Before you approve any step in your session, ask yourself two questions:

1. Does it match what I asked for? Downloading the address you gave it, looking at the file's header or running a count on planetas.csv are direct steps toward answering your question.
2. Does it only touch my practice folder? The command should only create or read files inside exoplanetas.

If both answers are yes, choose the option to approve it. Your session may propose the step with other tools: on Windows it sometimes uses a PowerShell command like Invoke-WebRequest instead of curl, or splits the download and the read into separate prompts. After downloading the file, it will ask permission to run a Python program that does the count, or even to install Python or pandas if you don't have them; you can approve that too. If it asks permission for something you don't understand, copy the prompt and ask your Maestro before approving.

What you should see at the end

Once you approve the step that counts the data, Claude Code gives you its final answer. In the October 31, 2026 test session it answered 74.2% (4,785 of 6,451 planets) and mentioned that the file had 40,350 rows.

NASA updates this catalog every week as new discoveries are confirmed, so it's normal to see a few more rows on your screen, some extra planets and a tiny change in the decimal. If instead you got something close to 89.8% (around 90%), the download worked fine, but your session counted the table's rows instead of unique planets. Hold on to that number, because on page 2.3 you'll see why that difference happens.

Also check your exoplanetas folder in your computer's file browser: the new planetas.csv file should be there. Keep it, because we'll work with it for the rest of the course. If the download fails or an error message appears, paste it into the chat with your Maestro to work through it step by step.

Try it

Run the whole session on your computer, approving each step after you read it. When Claude Code finishes, write below what it answered. Your Maestro will compare your numbers with the test session's to tell you whether your session counted planets or rows.