API

Without APIs, every tool is an island. A form builder does not know the CRM exists, and the CRM does not know a payment was made. A person fills the gap by copying data by hand, which is slow and error-prone. With APIs, a form submission can create a contact, start an email sequence and book a call within seconds.

For anyone building with AI, APIs are how an agent acts in the world. When an AI assistant sends an email or updates a deal, it is calling an API.

• Find the "API reference" in the tool's documentation, and check that the action you need is listed.
• Try no-code tools first. Zapier, Make and n8n call APIs for you.
• Store keys in a password manager or environment settings, never in a page, a document or a chat.
• Give each key the narrowest permissions it needs.
• Check the rate limit, which caps requests per minute.

Think of a restaurant. The menu lists what can be ordered and how, and the kitchen does the work behind the scenes. An API is the menu for a piece of software. It lists the requests another program may make, what to send with each one and what comes back. For instance, an accounting tool's API might allow "create an invoice for this customer" or "list the unpaid invoices". The answer usually comes back as structured text called JSON.

Most APIs need a key: a long secret string that identifies the caller and says what it is allowed to do.

• Pasting a live key into code that is later published.
• Assuming an API can do everything the app's screen can. Some features are not exposed.
• Not planning for the day the API is down or returns an error.

With an API, your system asks the other one. With a webhook, the other system tells yours the moment something happens. Most useful connections use both.