The annotation checks your object,

then forgets it.

const palette = { ink: '#e2e8f0', accent: [56, 189, 248] }

…: Palette

what tsc emits

declare const annotated: Palette;

✕ ink.toUpperCase() — TS2339
✕ accent no longer a 3-number tuple
✕ annotated.inkk — compiles fine

… satisfies Palette

what tsc emits

declare const satisfied: {
    ink: string;
    accent: [number, number, number];
};

✓ every one of the three

the check is identical put a number where a Colour belongs and both forms report TS2322 — satisfies is not the lenient option, it is the one that does not throw away your work

TypeScript 5.9 · --strict · type blocks copied from the declarations tsc emits for the demo

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