REST API
Definition
REST stands for representational state transfer, and it is a set of conventions rather than a strict standard. In a REST API the nouns are URLs, such as /files or /files/report-pdf, and the verbs are the HTTP methods applied to them. Requests and responses normally carry JSON, marked by a Content-Type header of application/json. The response status code tells you what happened before you read a single byte of the body: 200 for success, 201 when something was created, 401 when your credentials were wrong, 404 when the URL names nothing, 429 when you have sent too many requests. Every request stands alone and carries its own authentication, which is what makes the style straightforward to script and easy to cache.
Why It Matters
An API is what turns a manual chore into a line in a script. Uploading forty generated pages by hand is an afternoon; the same job as a loop of forty POST requests is a minute, and it can be re-run whenever the source changes. It also makes automation dependable in a way clicking never is, because the same call gives the same result and failures arrive as codes you can test for rather than a dialogue box someone closed. Skip that check and you get the classic silent pipeline: a script reporting success while every single upload came back 401.
How It Works
A client sends an HTTP request to an endpoint with a method, headers and sometimes a body. Authentication is normally a header reading Authorization: Bearer followed by an API token, so nothing secret sits in the URL where it would be written to logs. For a file upload the body is usually multipart form data, with the file in one field and metadata such as the desired name in another. The server answers with a status code and a JSON body, typically describing the created resource including the public URL it now lives at. Well-behaved clients check the status first, honour a Retry-After header on 429, and never assume a 200 means the body has the shape they expected.
Real-World Example
A studio generates a client report every Monday and wants it live without anyone opening a browser. A short script posts the HTML file to the hosting API with a name field of weekly-report, reads the address from the response, and drops that link into a team channel. The page at weekly-report.99helpers.site keeps the same address while its contents are replaced each week, and the previous version stays in history in case Monday's figures turn out to be wrong.
Common Mistakes
- ✕Putting the token in the query string — it then shows up in server logs, browser history and referrer headers
- ✕Parsing the body without checking the status code, so a 401 is read as an empty result and the run reports success
- ✕Retrying a failed call immediately in a tight loop; a 429 means slow down, and the response usually says for how long
Related Terms
API Token
A secret string that identifies your account to an API in place of a username and password. You send it with each request, and the service checks it and applies whatever permissions it carries.
Webhook
An HTTP request a service sends to a URL you provide when something happens on its side. Instead of you asking repeatedly whether an event has occurred, it tells you once, immediately.
MCP Server
A program that exposes a set of tools to an AI assistant over the Model Context Protocol. The assistant sees a list of actions it can take — read this, create that — and calls them during a conversation.
HTTP Status Code
An HTTP status code is the three-digit number a server returns at the head of every response, saying what happened to the request. It is the first thing on the first line — a 200 means here is the file, a 404 means there is nothing at that address.
Presigned URL
A presigned URL is a link to a private stored object that carries its own authorisation in the query string. Anyone holding the link can perform the one operation it was signed for, on the one object it names, until it expires.
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