API development
APIs your apps, partners, and AI tools can rely on.
Acasa Labs builds APIs: the backend behind your web and mobile apps, integrations with the third-party APIs your business runs on, public APIs with keys for your customers' developers, and MCP servers that let AI assistants use your product. We build them in FastAPI, Django REST Framework, or Node, documented and tested.
The problem
Every product is now an API with a few screens on top.
Your web app, your mobile app, your customers' systems, and now AI assistants all want to talk to your product. If the API was an afterthought, every new client means a new set of special cases. And the third-party APIs you depend on rate-limit you, change without notice, and fail at the worst time. An API that is designed for that is the cheapest part of the product to get right early.
What we build
- 01
Backend APIs for web and mobile
One versioned API behind every client, with typed models, OpenAPI documentation, and generated clients for your frontend.
- 02
Third-party integrations
Payment gateways, CRMs, social platforms, brokers, and accounting tools, wrapped so their outages, rate limits, and odd error codes do not reach your users.
- 03
Public APIs for your customers
API keys, scopes, rate limits per key, webhooks, and documentation a developer can use without emailing you.
- 04
MCP servers for AI assistants
A remote MCP server so ChatGPT, Claude, and Cursor can use your product on a user's behalf, with OAuth and properly scoped tokens.
From production
From APIs we run.
Living with someone else's API
PullsyPullsy pulls Instagram data through Meta's official sign-in. Meta's error codes are mapped to backoff with jitter, capped at 30 minutes, and re-authorization is handled as its own state instead of a failure. Pullsy also offers a REST API with keys for developers.
An MCP server with real auth
NoteTubeNoteTube's remote MCP server runs on Cloudflare Workers with OAuth, protected-resource metadata, and audience-checked tokens, so an AI assistant can only read the notes of the student who connected it.
A broker adapter under load
Options trading platformThe trading platform uses a custom adapter for the broker's REST and WebSocket APIs. Market-data decode runs on its own thread, so nothing blocking ever sits on the engine loop.
Write paths the public cannot reach
Siona JewelsOn Siona Jewels, enquiries are created only by a server action behind Turnstile, a honeypot, and a fill-time check. The public API cannot write them.
Honest trade-offs
When you do not need a separate API
A small internal tool used only in the browser can live happily as one Next.js or Django app with no public API. We add a separate, versioned API when a second client arrives: a mobile app, a partner, or an AI assistant.
What we reach for
- FastAPI, Django REST Framework, Node
- OpenAPI, generated clients
- OAuth 2.1, API keys, scoped tokens
- Webhooks with signatures and retries
- Redis rate limits and queues
- MCP servers on Cloudflare Workers
- pytest, contract tests
Proof
Shipped, not pitched.
01Our product
Pullsy
Instagram analytics that keep the numbers Instagram throws away.
Analytics for creators. Pullsy keeps insights Instagram discards after about 90 days, explains what each number means, grades the account, and turns it into a media kit a brand can verify.
Web · iOS (native SwiftUI) · REST API
02Our product
NoteTube
A lecture becomes a study system: chat, flashcards, quizzes, all grounded in the source.
An AI learning platform that turns PDFs, YouTube lectures, recordings, and notes into a structured notebook with grounded chat, spaced-repetition flashcards, and graded quizzes.
Web · iOS · Android · Chrome extension · MCP server
03Client work
Options trading platform
Microsecond market-data handling for index options, with risk checks that never sleep.
A private trading platform for index options on an Indian exchange: tick capture, research and backtesting, paper and live execution, and a control dashboard. Built for a client's internal use; details are anonymized.
Trading engine · Realtime gateway · Web dashboard
04Our product
SigmaCPM
Construction project management where AI reads the tender and shows its work.
One project record for civil contractors, from tender to closeout: bids, contracts, RFIs, vendor quotes, and drawings. The AI pulls line items and bond terms out of tender PDFs and cites the page for every value.
Web · API · Chrome extension
Questions
API development questions we get asked.
REST, GraphQL, or something else?
REST with an OpenAPI schema for most products, because every client and tool understands it. We use WebSockets or server-sent events for live data, and GraphQL only when many clients need very different shapes of the same data.
Can you integrate with an API that has poor documentation?
Yes. That is most of them. We build a small adapter around it, record real responses in tests, and handle the errors it actually returns, not the ones the docs list.
What is an MCP server and do we need one?
The Model Context Protocol lets AI assistants like ChatGPT, Claude, and Cursor call your product as a tool. If your customers would ask an assistant to do something in your product, an MCP server makes that possible, with their permission.
How do you secure a public API?
Keys or OAuth tokens with scopes, rate limits per key, input validation at the edge, and audit logs. Write paths that should never be public are not exposed at all.
Will you document the API?
Yes. The OpenAPI schema is generated from the code, so the documentation cannot drift from what the API does.
API development
Tell us what needs to talk to what.
Your apps, your partners, the APIs you depend on. We will sketch the API and the integrations and tell you what it would take.