Updated 2026-10-21 · RobotBase MCP · 72 tools · one remote endpoint
x402 MCP server: pay per call without an API key
Short answer: RobotBase gives every caller a free daily allowance, then returns HTTP 402 with machine-readable accepts[] terms for paid tools. The caller pays prepaid USDC credits over x402 (USDC on Base or Solana) from its own wallet; there is no API key, account or subscription, and the endpoint never holds funds.
How the payment flow works
- The agent calls a metered tool, e.g.
web_search or cyberlibrary_fulltext_search.
- While the free daily allowance lasts, the call returns normally with a
_metering block.
- When the allowance is exhausted, the tool returns HTTP 402 Payment Required with machine-readable
accepts[] terms: network, asset, amount, pay-to address and the credit pack.
- The caller's wallet pays USDC on Base or Solana through an x402 facilitator; the credit is recorded against the payer address.
- The agent retries the call; the paid credit is spent and the result is returned.
What is metered
| Area | Free allowance | Paid |
|---|
| Verification (44 tools) | free forever | — |
| All 10 web tools | 100 calls/IP/day shared | 1–3 credits |
| Risk + CyberLibrary | 5 calls/IP/day shared | 1–5 credits |
Credit packs: 10 credits / 0.10 USDC or 100 credits / 1.00 USDC. No account, no subscription, no API key; the endpoint never holds funds or takes custody. Base and Solana are payment rails only — no Base/Solana chain data is served.
Why an agent can use it without a human
- The 402 response is machine-readable, so an agent can decide to pay or stay within free tools.
- Credits are prepaid, so there is no per-request signing or wallet pop-up.
- The free tier needs no wallet at all, which keeps evaluation and CI cheap.
Example
Use web_search for "x402 MCP payments", then fetch the best result.
If the tool returns 402, report the accepts[] terms instead of retrying blindly.
FAQ
What is x402 in MCP?x402 is an HTTP 402-based payment flow: the server returns machine-readable payment terms and the caller pays per call, instead of buying an API key or subscription. RobotBase uses x402 only after free daily allowances are used.
Do I need a wallet to try RobotBase?No. The free tier needs no wallet, account or API key. A wallet is only needed for credit packs after the free allowance.
Which networks can pay?USDC on Base or Solana. Those are payment rails only; RobotBase serves no Base or Solana chain data.
How much does a call cost?Web search and fetch-family calls cost 1 credit; risk is 1 credit; CyberLibrary retrieval is 1–2 credits and full-text search 5. Packs are 10 credits / 0.10 USDC or 100 credits / 1.00 USDC.
Does RobotBase hold my funds?No. Payment goes to the pay-to address in the 402 terms; RobotBase records credits but never takes custody or signs for the caller.