Firebase Cloud Firestore triggers for Cloud Functions : context.params undefined - node.js

Question

This should be simple but I am not sure what I am missing.
I am trying to recreate the example stated in the docs, modifying only the variable names:
https://firebase.google.com/docs/functions/firestore-events
Trying to log the value of context.params returns undefined.
const functions = require("firebase-functions");
exports.makeUppercase = functions.firestore
.document("/messages/{documentId}")
.onCreate((snap, context) => {
console.log(context.params.documentId); // undefined
console.log(context.params); // undefined
});
package.json
{
"name": "my-app",
"version": "0.1.0",
"private": true,
"dependencies": {
"#emotion/react": "^11.4.1",
"#emotion/styled": "^11.3.0",
"#mui/icons-material": "^5.0.0",
"#mui/material": "^5.0.0",
"#mui/styles": "^5.0.0",
"#mui/x-data-grid": "^4.0.0",
"#testing-library/jest-dom": "^5.14.1",
"#testing-library/react": "^11.2.7",
"#testing-library/user-event": "^12.8.3",
"firebase": "^9.0.2",
"lodash": "^4.17.21",
"react": "^17.0.2",
"react-dom": "^17.0.2",
"react-firebase-hooks": "^3.0.4",
"react-redux": "^7.2.5",
"react-router-dom": "^5.3.0",
"react-scripts": "4.0.3",
"redux": "^4.1.1",
"redux-thunk": "^2.3.0",
"uuid": "^8.3.2",
"web-vitals": "^1.1.2"
},
"scripts": {
"start": "react-scripts start",
"build": "react-scripts build",
"test": "react-scripts test",
"eject": "react-scripts eject"
},
"eslintConfig": {
"extends": [
"react-app",
"react-app/jest"
]
},
"browserslist": {
"production": [
">0.2%",
"not dead",
"not op_mini all"
],
"development": [
"last 1 chrome version",
"last 1 firefox version",
"last 1 safari version"
]
},
"devDependencies": {}
}
What am I missing here? Thanks a lot!