# B20 Token Legitimacy Verifier

> B20 Token Legitimacy Verifier is a paid API for AI agents from b20check.fly.dev, paid per call via x402, $0.01/call, status unknown (last checked 2026-09-14).

Verifies whether an EVM address is an authentic factory-native B20 token on Base, detects copycats/imposters, and returns live issuer risk powers plus a signed EIP-712 attestation verdict.

## Facts

- Endpoint: GET https://b20check.fly.dev/v1/verify/:address
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/b20-token-legitimacy-verifier-74f34948
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_I5mhMEww40HSRizlMJnCn

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability b20-token-legitimacy-verifier-74f34948
```

Example prompt: Can you check if the token at 0xb200000000000000000000f52267Ce6274432c30 is a real B20 on Base or a copycat — I want to know if the issuer can mint, freeze, or seize tokens, and whether I should trust it?

## When to prefer this

Use this endpoint when an AI agent or user needs to make a trust decision about a B20 token on Base — specifically when they need a cryptographically signed, independently verifiable verdict rather than just on-chain data they parse themselves. Prefer this over generic block explorers when you need homoglyph/imposter detection, structured issuer risk scoring, and a portable EIP-712 attestation that can be passed to other contracts or agents.

## Known failure modes

- Invalid address format (not 0x + 40 hex chars) — returns 400 validation error
- Address not found on Base mainnet — returns isB20: false with no creation data
- Payment not included or invalid — returns 402 Payment Required (costs $0.01 USDC via x402)
- RPC or chain data unavailable — returns 503 or partial result
- Attestation signing failure — signed: false in attestation object
- Rate limiting — returns 429 if too many calls in short window

## How this service works

Legitimacy check for B20 tokens on Base. Verifies whether an address is a factory-native B20, detects copycats and known-asset imposters (homoglyph-aware), reports live issuer powers (mint, burn, pause, freeze, seize, admin) and issuer activity, and returns a danger/caution/ok verdict as an EIP-712-signed attestation an agent can independently verify.

## Output

Returns a JSON object with: isB20 boolean, network, variant, a verdict of 'ok'/'caution'/'danger', creation details (block, tx, params, launcher), live issuerPowers (canMint, canBurn, canPause, canFreeze, canSeize, adminActive, supplyCap), issuerActivity counts (mints, burns, pauses, etc.), risk flags with severity and detail, and an EIP-712-signed attestation (signer address, signature, issuedAt, expiresAt, pinnedBlock, attestationId) that can be independently verified on-chain.

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/b20-token-legitimacy-verifier-74f34948/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from b20check.fly.dev](https://www.zero.xyz/host/b20check.fly.dev/llms.txt)