What is a call?

A call is one question you send to the gateway and the one answer you get back. Ask “how much SOL is in this wallet?” and you get the number. That round trip is one call.

What one looks like

Each kind of question has its own tool. You send the details as JSON, and the answer comes back as structured data a program or AI agent can read.

The question

POST https://trade-desk-1021990235790.us-central1.run.app/api/tools/balance
{ "wallet": "<wallet_address>" }

The answer

{
  "wallet": "<wallet_address>",
  "network": "mainnet-beta",
  "lamports": "1500000000",
  "sol": "1.5",
  "slot": 455508107
}

AI agents make the same calls over MCP: instead of a web address, the agent picks a tool by name, such as balance, and gets the same answer.

What calls cost

Every tool, including this balance call, gives each caller 25 free calls a day, then costs $0.01 in USDC ($0.02 for the three safety checks), paid with the request itself through x402. Calls that end in an error are never charged and never use up a free call.

How a call travels: think of a restaurant

In a restaurant	In the gateway
The customer wants something	The client: your app or AI agent
The menu lists every dish	The API: the list of tools and how to ask
A dish has its own name	An endpoint: one address, one job, like `/api/tools/balance`
The cashier checks you can order	Free calls and payment: counts free calls, then checks the x402 payment
The chef cooks	The logic: validates inputs and does the work
The supplier delivers ingredients	The blockchain: Solana, read live
The plate arrives	The response: structured JSON, usually in well under a second

Glossary

Term	Meaning
API	Everything the gateway can do and the format for asking.
Endpoint	A single address that does one job.
Request / response	What you send, and what comes back.
MCP server	A menu written for AI agents, so they can find and call tools themselves.
x402	An open standard for paying per request, here in USDC on Solana.

Make your first call