Summary Table: Environment Setup Checklist

7.2 Setting Up the API Project (Express or FastAPI)

Before Claude can help you design and implement endpoints, you need a clean, runnable project skeleton. This section gives you two equally valid starting points: Express (Node.js) or FastAPI (Python). Each starter includes a health check and a minimal in-memory tasks API so you can confirm the runtime, exercise Claude’s suggestions, and grow the service incrementally. Pick one stack and get it running in a few minutes; all code here is complete and self-contained.

Concept Development

Choose your stack based on team familiarity and ecosystem needs. Express offers a tiny surface area with maximal flexibility in the Node.js ecosystem. FastAPI provides first-class data validation via Pydantic and automatic OpenAPI docs, making schema-driven development natural. Whichever you choose, keep the first commit small: a single process, in-memory storage, and a straightforward route layout. That simplicity makes it easy for Claude to reason about behavior, generate tests, and refactor confidently.

Hands-On Example A: Express (Node.js)

Create a new folder, then add these two files. This starter uses only core Express and the built-in JSON body parser. It provides/health plus/tasks CRUD with minimal validation.

package.json

{
  "name": "taskflow-express",
  "version": "1.0.0",
  "description": "TaskFlow API starter (Express)",
  "main": "index.js",
  "type": "module",
  "scripts": {
    "start": "node index.js",
    "dev": "node --watch index.js",
    "test": "node -e \"console.log('Add tests later')\""
  },
  "dependencies": {
    "express": "^4.19.2"
  }
}

index.js

import express from "express";

const app = express();

const PORT = process.env.PORT || 3000;

app.use(express.json());

// In-memory store

let nextId = 1;

const tasks = new Map(); // id -> { id, title, description, completed }

// Health check

app.get("/health", (_req, res) => {
  res.json({ status: "ok", service: "taskflow-express" });
});

// Create task

app.post("/tasks", (req, res) => {
  const { title, description = "", completed = false } = req.body || {};

  if (typeof title !== "string" || !title.trim()) {
    return res.status(400).json({ error: "title is required" });
  }

  const task = { id: nextId++, title: title.trim(), description, completed: !!completed };

  tasks.set(task.id, task);

  res.status(201).json(task);
});

// List tasks

app.get("/tasks", (_req, res) => {
  res.json({ items: Array.from(tasks.values()) });
});

// Get task by id

app.get("/tasks/:id", (req, res) => {
  const id = Number(req.params.id);
  const task = tasks.get(id);

  if (!task) return res.status(404).json({ error: "not found" });

  res.json(task);
});

// Update task (full update)

app.put("/tasks/:id", (req, res) => {
  const id = Number(req.params.id);

  if (!tasks.has(id)) return res.status(404).json({ error: "not found" });

  const { title, description = "", completed = false } = req.body || {};

  if (typeof title !== "string" || !title.trim()) {
    return res.status(400).json({ error: "title is required" });
  }

  const updated = { id, title: title.trim(), description, completed: !!completed };

  tasks.set(id, updated);

  res.json(updated);
});

// Patch task (partial update)

app.patch("/tasks/:id", (req, res) => {
  const id = Number(req.params.id);
  const current = tasks.get(id);

  if (!current) return res.status(404).json({ error: "not found" });

  const { title, description, completed } = req.body || {};

  if (title !== undefined && (!title || typeof title !== "string")) {
    return res.status(400).json({ error: "title must be a non-empty string when provided" });
  }

  const updated = {
    ...current,
    ...(title !== undefined ? { title: title.trim() } : {}),
    ...(description !== undefined ? { description } : {}),
    ...(completed !== undefined ? { completed: !!completed } : {})
  };

  tasks.set(id, updated);

  res.json(updated);
});

// Delete task

app.delete("/tasks/:id", (req, res) => {
  const id = Number(req.params.id);

  if (!tasks.has(id)) return res.status(404).json({ error: "not found" });

  tasks.delete(id);

  res.status(204).send();
});

app.listen(PORT, () => {
  console.log(`TaskFlow (Express) running on http://localhost:${PORT}`);
});

Run it

npm install
npm run start

Visit http://localhost:3000/health. Create a task:

```bash
curl -s -X POST http://localhost:3000/tasks \
-H "Content-Type: application/json" \
-d '{"title":"First task","description":"Try Claude prompts"}'

Hands-On Example B: FastAPI (Python)

Create a new folder and add the following two files. This starter uses FastAPI with Pydantic models and includes/health plus/tasks CRUD. It is fully typed and returns consistent JSON responses.

requirements.txt

fastapi==0.114.0
uvicorn==0.30.5

app.py

from typing import List, Optional, Dict

from fastapi import FastAPI, HTTPException

from pydantic import BaseModel, Field

app = FastAPI(title="TaskFlow FastAPI", version="1.0.0")

class TaskCreate(BaseModel):
    title: str = Field(min_length=1)
    description: Optional[str] = ""
    completed: bool = False

class Task(TaskCreate):
    id: int