Anthropic Claude Sonnet 5

Explain what an API is to someone who has never written code. Do not use a restaurant or waiter analogy. Plain prose only — no headings, bullet points, or markdown formatting. Maximum 50 words.

An API is a set of rules that lets two computer programs talk to each other. One program offers certain services or information, and the API defines exactly how another program can request them—what to ask for, how to ask, and what kind of answer to expect back.

A two-person startup is deciding whether to build their own user authentication or use a hosted provider. Give them a clear recommendation, then the single strongest argument against your own recommendation. Plain prose only — no headings, bullet points, or markdown formatting. Maximum 150 words.

Use a hosted authentication provider (like Auth0, Clerk, Supabase Auth, or Firebase Auth). For a two-person team, engineering time is the scarcest resource you have, and authentication is a solved problem with enormous security surface area—password resets, session management, MFA, OAuth flows, token security, compliance requirements. Building this yourselves means spending weeks on undifferentiated infrastructure instead of your actual product, and any subtle bug in a homegrown auth system can lead to a catastrophic breach that kills a young company's reputation instantly. Hosted providers have dedicated security teams, handle edge cases you haven't thought of, and let you ship auth in days rather than weeks. The strongest counterargument: hosted auth creates a critical dependency and recurring cost that scales with users, and migrating away later—once you're deeply integrated and have thousands of accounts—can be far more painful and risky than if you'd built on flexible, self-owned infrastructure from the start.