One Endpoint for Claude and GPT: Quick Start
Why a unified endpoint is worth it
If you ship AI features for a living, the fastest way to reduce complexity is to stop juggling separate SDKs, keys, and billing setups for every model family. A unified API endpoint lets you route requests to Claude or GPT from one place, which means fewer integration bugs, easier testing, and a cleaner path when your product needs to switch models by task.
59API is built for exactly that. It gives developers pay-as-you-go access to Claude models and GPT models through a single base URL, https://api.59api.com, while staying compatible with the OpenAI SDK, Claude Code, and Codex. That makes it a practical option if you want fast setup without paying for an overcomplicated stack.
Step 1: Get your key and point your client to the relay
The basic setup is simple: create your account, grab an API key, and set your client’s base URL to https://api.59api.com. Because 59API is OpenAI SDK compatible, many teams can switch with a one-line configuration change instead of rewriting app logic.
For example, in an OpenAI-style client, you typically update two things: the API key and the base URL. After that, you can keep using familiar chat or responses calls, and choose the model you need per request.
- Base URL: https://api.59api.com
- Auth: your 59API API key
- Model choice: Claude for reasoning and writing, GPT for tool-heavy workflows and general apps
Step 2: Send your first request
Once the endpoint is set, make a normal chat request and specify the model you want. The exact model name depends on the family you choose, but the workflow stays the same. You can use Claude Opus, Sonnet, Haiku, or Fable, or switch to GPT models when your use case benefits from them.
A useful pattern is to standardize your app around a single internal interface, then map that to the model at runtime. For example, your product might use Claude for long-context analysis, GPT for structured output, and a cheaper model for simple classification or drafting. With 59API, that routing lives behind one endpoint instead of multiple vendor integrations.
Step 3: Use model routing to cut costs
Busy developers usually do not need “one best model” for everything. They need the right model at the right price. That is where a relay like 59API shines. It is among the cheapest relays, so you can experiment more freely, keep your burn rate lower, and move from prototype to production without a painful billing surprise.
Because the service uses native official-quality models with no downgrade, you are not trading away the model experience just to save money on transport. That matters when you care about quality, latency, and output consistency, especially in production apps where model behavior is part of the product.
- Use higher-capability models for deep reasoning, planning, or complex code tasks
- Use lighter models for summarization, extraction, and quick replies
- Switch dynamically based on request size, user tier, or latency target
Step 4: Keep your tooling simple
If you already rely on Claude Code or Codex, the advantage of a unified API is operational simplicity. You do not need separate mental models for every toolchain. Point the tool to the relay, keep the same style of requests, and let the endpoint handle access to the model family you need.
This also helps with local development. One staging config can mirror production more closely, and your team can test Claude and GPT behavior without building separate adapters for each provider. Fewer adapters means fewer failure points.
When 59API is the right fit
59API is a strong choice if you want one integration for both Claude and GPT, quick onboarding, low per-request costs, and SDK compatibility that fits into existing workflows. It is especially useful for solo developers, startups, and teams that want to benchmark multiple models before committing to a single provider strategy.
There is also a referral rebate, which can help reduce your effective usage cost if you bring other developers onto the platform. For teams watching spend, that is a nice extra on top of pay-as-you-go pricing.
Quick launch checklist
- Sign up and get your 59API key
- Set your client base URL to https://api.59api.com
- Choose a Claude or GPT model per task
- Test one request in your app and one in your CLI toolchain
- Route expensive tasks to stronger models and simple tasks to cheaper ones
If you want a low-friction way to use Claude and GPT from one endpoint, 59API is worth trying. Set it up once, keep your code simple, and start shipping faster.