Building your own product
One dependency
instead of twelve
The usual product is a keyring: a verification vendor, a conversion library, a scraping service, six OAuth apps, an auth provider, a billing SDK and a payments processor. castomAPI is the argument that a developer can have all of it behind one key, one wallet and one invoice — and keep the parts that are actually theirs.
Three things in one place
Simplification
One header, one envelope, one error shape, one ledger. A new capability is a new path, not a new vendor. The spec is one document you can generate a client from.
Security
Tenancy by key and project. Custom code in isolated V8 with a real network policy. Encrypted platform tokens. Misses that leak nothing. The security page lists each claim.
Ease of use
1000 free tokens a month means the first version never needs a card. Every endpoint page here has a mock tester; the live docs run the real thing.
Extensibility
When the catalogue stops, write the endpoint: JavaScript at /c/your-slug, billed like the rest. The custom-endpoints service →
Reach
Export any set of endpoints as n8n or Make nodes, expose them to Zapier, or hand the whole catalogue to an agent over MCP.
What you do not have to build
Sign-in
Password, Google, GitHub, Apple. Sessions every service verifies. Projects that keep tenants apart. Or "Sign in with castomo" for your users through OAuth.
Plans and entitlements
Declare plans; Billing mints the Stripe prices, runs checkout and the portal, and hands your product an entitlement to read.
Taking money
Charge a customer on a seller's behalf through Stripe Connect. Refunds and payouts by the seller's rules.
Bookings
Resources, slots, reservations, reminders, cancellation policies as data.
Documents
Per-project JSON storage with a schema you declare and erasure that fans out when an account is deleted.
Presence
Cursors, shared state and chat between people on the same page, over WebSockets, revocation-aware.
Pictures with licences
Royalty-free media across eleven providers, imported with the credit line the licence demands.
Uptime
One-minute checks, incidents, alert channels — for your product's own targets.
The first hour
Mint a key
Sign in at the dashboard, create a key. It is shown once.
Make the first call
Any endpoint page here — try Verify — has curl, JavaScript, Node, Python and PHP ready to paste.
Register a project
If your product has users, a project in Auth keeps them yours and gives you sign-in for free.
Read the ledger
GET /wallet/ledger shows what the hour cost, by endpoint. Usually: a few tokens out of a thousand.
/v1/verify/email1 token{ "email": "ada@example.com" }{
"status": "success",
"valid": true,
"syntax": true,
"mx": true,
"disposable": false,
"role": false,
"suggestion": null,
"tokensDeducted": 1
}Longer notes
Questions
Is there an SDK?
The spec is OpenAPI 3; generate a client in any language from docs/json. The Ecosystem export endpoint generates n8n and Make packages; the Zapier group and the MCP server cover the other two doors. A plain fetch is enough for most products.
What happens when my users hit the rate limit?
Limits are per castomAPI account — yours — not per end user. Pro and Enterprise tiers raise the per-minute quota; custom endpoints and batch operations reduce the number of calls a workflow needs.
Can I run it myself?
Not today. The platform runs on the ecosystem's own EU boxes; the reference-data service is deliberately built to survive on shared hosting. Self-hosting is a question to ask, not a page to link.
Where do my users' platform tokens live?
Encrypted, in the platform's database, scoped to your project, refreshed on demand, deleted when the user disconnects or the account is erased.