# EVM Signature V Classifier

> EVM Signature V Classifier is a paid API for AI agents from api.delx.ai, paid per call via x402, $0.001/call, status unknown (last checked 2026-09-15).

Classifies an EVM transaction signature V value as legacy, EIP-155, or other type, given the V integer and chain ID.

## Facts

- Endpoint: POST https://api.delx.ai/api/v1/x402/evm-signature-v-classify
- Price: $0.001/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/evm-signature-v-classifier-c34f6e96
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_pvf6KHrj3KBubiykLGOwj

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 evm-signature-v-classifier-c34f6e96 -d '<json body>'
```

Example prompt: Classify this EVM signature V value for me — V is 27 and the chain ID is 8453. Is it a legacy signature or EIP-155?

## When to prefer this

Use this endpoint when an AI agent needs to programmatically determine the signing scheme of an EVM transaction's V parameter — particularly during transaction pre-flight checks, wallet debugging, or when building cross-chain transaction relayers. It is preferred over manual lookup when the agent must handle multiple chains or legacy vs EIP-155 signatures dynamically. Ideal for agents that process raw transactions and need to validate signature encoding before broadcasting.

## Known failure modes

- Missing or invalid V integer returns a validation error
- Missing or invalid chain_id returns a validation error
- V value inconsistent with any known classification may return an unexpected or unrecognized classification
- Network or service unavailability returns a 5xx error

## How this service works

EVM Signature V Classify: EVM Signature V Classify classifies common signature recovery and EIP-155 v values from bounded caller-supplied values without an external provider. Call EVM Signature V Classify before signing, submitting, replacing, or accepting an EVM/Base transaction assembled from caller-owned data. Returns normalized transaction evidence, calculated budget or shape findings, and a fail-closed preflight status for EVM Signature V Classify as versioned deterministic JSON. Price: $0…

## Output

Returns a JSON object containing the original V value, a classification string (e.g. 'legacy', 'eip155'), the expected chain ID derived from V, operation name, status ('pass'/'fail'), and an evidence block confirming no data was retained and no external calls were made.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "v": {
   "type": "integer",
   "description": "V supplied to EVM Signature V Classify; used only for this bounded calculation and processed in memory without retention."
  },
  "chain_id": {
   "type": "integer",
   "description": "Chain Id supplied to EVM Signature V Classify; used only for this bounded calculation and processed in memory without retention."
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "result": {
   "v": 27,
   "classification": "legacy",
   "expected_chain_id": 8453
  },
  "schema": "delx/util-evm-signature-v-classify/v1",
  "status": "pass",
  "evidence": {
   "retained": false,
   "input_sha256": "7717f04f6d982d96f99fcfa69caef99e8c3090309ae581ae53da0c8612700635",
   "external_calls": 0
  },
  "operation": "evm_preflight:evm_signature_v_classify"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/evm-signature-v-classifier-c34f6e96/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.delx.ai](https://www.zero.xyz/host/api.delx.ai/llms.txt)