MCP vs REST vs SDK for Social Media Integrations

Pick the integration method by asking one question: who or what is making the call? If it is an AI agent that should decide what to do, you want MCP. If it is your own backend or a script that already knows the exact request, you want REST. If it is app code in a language with a good client library, you want an SDK. That is the whole decision. Everything below is the reasoning, the tradeoffs, and a real code snippet for each, checked against PostSider’s docs.

I build a social media publishing tool that exposes all three on purpose, so I have had this argument with a lot of developers. The mistake almost everyone makes is treating MCP, REST, and SDK as rivals where one wins. They are not rivals. They are three doors into the same room. The actions behind them (list channels, schedule a post, upload media, read analytics) are identical. What changes is the caller and what that caller finds convenient.

The three are layers, not competitors

An SDK wraps a REST API. An MCP server usually wraps that same REST API too. All three call the same underlying actions. The difference is who holds the steering wheel.

Here is the stack, bottom to top. At the base is a set of actions the platform can perform: create a post, schedule it, upload an image, fetch analytics. REST is the thinnest public skin over those actions, plain HTTP with JSON. An SDK is a typed library that calls that REST API for you and hands your code real objects and methods. MCP is a tool-calling layer, also usually sitting on the REST API, that lets an AI model discover the available actions and call them in natural language.

Once you see the layering, the “which is better” question dissolves. You do not choose the best layer. You choose the layer that matches your caller. A shell script has no use for an SDK’s type system. An AI agent has no patience for you to hand-write HTTP. Typed app code does not want to build request bodies by hand. Same engine, three grips.

Use MCP when an AI agent is the one deciding

MCP is for callers that reason. The agent reads the tool list, learns each tool’s schema at runtime, and calls the right one to satisfy a goal you gave it in plain language. You write no request code.

The Model Context Protocol is a standard that lets an AI model discover and call external tools through a uniform interface. It went from an Anthropic experiment to shared infrastructure fast. By the December 2025 donation to the new Agentic AI Foundation, Anthropic reported more than 10,000 active public MCP servers and 97M+ monthly SDK downloads across Python and TypeScript, with the foundation co-founded by Anthropic, Block, and OpenAI and backed by Google, Microsoft, AWS, Cloudflare, and Bloomberg. When OpenAI, Google, and Microsoft all sponsor the same protocol, it has stopped being one vendor’s idea and become the wire agents speak. If you want the wider context on this shift, I wrote about AI agents in social media marketing, and there is a plain explainer of what an MCP server actually is.

The reason MCP is a genuinely different integration path, not just REST with extra steps, is discovery. With REST you read the docs, you hardcode the endpoint, you build the body. With MCP the agent asks the server what it can do, gets back a machine-readable schema for every tool, and picks. PostSider’s MCP server exposes 16 tools to the agent according to its MCP docs, covering channel listing, scheduling, media, analytics, and connector auth. The agent calls integrationList, then integrationSchema, then schedulePostTool, with no glue code from you.

Connecting is a URL and a key, not a build step. Here is the real setup for Claude Code against PostSider:

# Point any MCP client at PostSider and pass your API key.
claude mcp add --transport http postsider \
  https://api.postsider.com/mcp \
  --header "Authorization:Bearer your-api-key"

After that you do not write an integration. You say “schedule a post to X for tomorrow at 10am: our new feature is live” and the agent picks the tools. Use MCP when the caller should choose the action. Do not use it as a backend transport for code you already wrote, that is what REST is for, and routing deterministic code through an LLM just adds latency, cost, and a chance the model does something you did not ask for. If you want the deep version of this, see driving social media from an AI agent with MCP.

Use REST when your code already knows the exact request

REST is the base layer, and the right pick when the caller is deterministic. Your code knows which endpoint, which body, which time. There is no decision to delegate, so you want the thinnest, most portable path with no extra dependency.

REST wins on three things: it works from any language that can make an HTTP request, it has zero install footprint, and it always exposes the newest endpoint the moment the platform ships it (an SDK often lags the API). A cron job in bash, a Cloudflare Worker, a Go service, a Zapier step, a five-line Python glue script: all of them speak HTTP, none of them need a library. This is why a raw REST call is the fastest thing to ship for a one-off.

PostSider’s Public API is plain HTTP with JSON at https://api.postsider.com/public/v1, authenticated with an Authorization header (API docs). One POST /posts request schedules a post; type is now, schedule, or draft. Here is a real scheduled post to X:

curl -X POST "https://api.postsider.com/public/v1/posts" \
  -H "Authorization: your-api-key" \
  -H "Content-Type: application/json" \
  -d '{
    "type": "schedule",
    "date": "2026-07-01T10:00:00.000Z",
    "shortLink": false,
    "tags": [],
    "posts": [{
      "integration": { "id": "your-integration-id" },
      "value": [{ "content": "Hello from the PostSider API!", "image": [] }],
      "settings": { "__type": "x", "who_can_reply_post": "everyone" }
    }]
  }'

The tradeoff you accept with REST is that you build and maintain everything by hand: request bodies, retries, pagination, error mapping, media upload as multipart. PostSider softens the sharp edges, a 60 requests per minute per organization rate limit with X-RateLimit-Remaining headers, an Idempotency-Key header so a retried POST /posts within 24 hours returns the original result instead of double-posting, and standard status codes. Those are documented, but you still wire them up yourself. If your caller is a machine that already knows the plan, that control is a feature. There is a full walkthrough in schedule posts with a social media API.

Use an SDK when you want the compiler on your side

An SDK is REST with the boring parts done for you. In a supported language, you get typed methods, autocomplete, and helpers for the annoying bits (multipart upload, webhook signature verification) so you write less and break less.

The value of an SDK is the developer experience, not new power. It cannot do anything REST cannot, because it calls REST underneath. What it buys you is that your editor knows the shape of a post before you run the code, a typo in a field name is a red squiggle instead of a 400 at runtime, and common tasks collapse to one method call. PostSider ships an official TypeScript client. The setup and a scheduled post look like this (SDK reference):

import Postsider from '@postsider/node';

const client = new Postsider(process.env.POSTSIDER_API_KEY);

// List channels, then schedule a typed post to the first one.
const channels = await client.integrations();

await client.post({
  type: 'schedule',
  date: '2026-07-01T09:00:00.000Z',
  shortLink: false,
  tags: [{ value: 'launch', label: 'Launch' }],
  posts: [{
    integration: { id: channels[0].id },
    value: [{ content: '<p>Excited to share our new feature</p>', image: [] }],
    settings: { __type: 'x' },
  }],
});

The published package is @postsider/node. The tradeoffs cut the other way from REST. An SDK is a point-in-time snapshot of the API, so when the platform ships a new endpoint the library may not cover it yet, and you either wait for an update or drop back to REST for that one call (this tradeoff is well described by Waldek Mastykarz). It also only exists for the languages that were built, and it adds a dependency you have to keep current. Reach for the SDK when you are writing app code in a language it supports and you value speed and safety over zero dependencies. Skip it for a quick script or an unsupported stack, where REST is simpler.

The decision, on one screen

The whole comparison collapses to a small table. Match the row to your caller and stop overthinking it.

	MCP	REST	SDK
Best caller	AI agent that decides	Backend or script that already knows	Typed app code in a supported language
Who picks the action	The model, at runtime	Your code, ahead of time	Your code, ahead of time
Language support	Any MCP client	Any language with HTTP	Only languages with a published SDK
Setup cost	Point client at a URL, pass a key	Write the HTTP calls yourself	Install a package, call methods
Newest endpoints	As the tools are exposed	Immediately	Whenever the SDK is updated
You maintain	Nothing, the client does it	Bodies, retries, pagination, uploads	Keep the dependency current
Main risk	Model does something unasked	More boilerplate, more to get wrong	Version lag, limited languages

A useful gut check: if the caller can read documentation and decide, use MCP. If the caller is a program that already made the decision, use REST, or an SDK if there is a good one for your language. The three are not ranked. They are matched.

Why one platform ships all three

A serious platform exposes every layer because it does not get to choose its callers. Some integrations are AI agents, some are cron jobs, some are typed services, and a single team often runs all three against the same account.

This is the founder opinion the rest of the article was building to. When people ask why PostSider bothers with MCP and REST and an SDK instead of picking one, the answer is that “pick one” is a bet on who your users are, and it is a bet you lose. The solo builder wiring a nightly script wants curl. The agency shipping a Next.js dashboard wants types and autocomplete. The person who just wants their AI assistant to run their accounts wants to paste a URL and a key and never see an endpoint. Force any of them down the wrong door and you have lost that integration. So all three read the same channels, act on the same posts, and authenticate with the same key from Settings > Developers > Public API. Mixing them in one project is the normal case, not an edge case: start an account, then let your backend use the SDK, your analytics job hit REST, and your agent drive the same posts over MCP.

That is the actual information gain here. The question is never “MCP or REST or SDK.” It is “who is calling, and what is convenient for them,” asked once per integration. Answer that, and the layer picks itself.

If you are building agent workflows on top of this, the PostSider docs cover the API, the MCP server, and the SDKs in full, and the developers page is the fastest way in. Pick your door by your caller, not by the changelog.