An AI agent builder, and the part that decides whether it works

An AI agent builder is only as useful as the tools it can hand an agent, so the hard part of building one is not the prompt or the loop but deciding what it can actually reach and what happens when a tool answers slowly, wrongly, or not at all.

An agent builder lets you describe what an agent should do and wires up the loop: a model, some tools, and a way to keep going until the job is finished.

The loop is the easy part

Model, tools, repeat until done. Every agent framework implements roughly the same loop and none of them differ much in how well they do it. If your agent is disappointing, the loop is almost never the reason.

It is the tools that decide what an agent can do

A tool is an interface you design, not a capability you switch on. Its name decides whether the model reaches for it at the right moment, its return shape decides whether the next step is sensible, and what it says on failure decides whether the agent recovers or starts inventing. Most of the work in building an agent sits in those three decisions, and none of them is in the prompt.

What a tool must tell an agent when it fails

More than an error. An agent that receives 'request failed' will usually retry, and retry again, and eventually invent a plausible answer. A tool that says which part failed, whether retrying could help, and how stale its data is gives the agent something to reason with. Most tool failures that look like model failures are actually this.

What we expose, and what we deliberately do not

Twenty three public read endpoints covering prices, order books, funding and equities, with no key required, so an agent can be given market access without being given credentials. Anything that moves money needs a key and a human decision behind it. That split is deliberate: read access is cheap to grant and hard to misuse, and the two should never be bundled.

Live, right now, on this page

Market	Price	Funding	24h volume
BTC	$81,925.50	0.0013%	$527,507,794
ETH	$2,431.95	0.0013%	$292,050,147
SOL	$104.51	0.0013%	$80,798,016
HYPE	$81.42	0.0013%	$12,273,803

Read from a live market as this page rendered, through a public endpoint that needs no key. Read at 2026-10-14 20:20 UTC; accurate as of that time and not afterwards.

Describe something and watch it get built.

Open the builder, or start from a working app and change it.

Common questions

What decides whether an AI agent works?

The tools you give it, not the loop or the prompt. Every framework implements roughly the same loop. An agent with search and a calculator can answer questions, while one that can read a live order book and check a balance can do a job.

Why do AI agents invent answers when a tool fails?

Because the tool said too little. An agent told only that a request failed will retry and eventually produce a plausible answer. A tool that says which part failed, whether retrying could help and how stale its data is gives the agent something to reason with.

Should an agent get read and write access together?

No. Read access is cheap to grant and hard to misuse, while anything that moves money needs a key and a human decision. Keeping the two separate means an agent can be given market access without being given credentials.