# EVM Next Base Fee Bound

> EVM Next Base Fee Bound is a paid API for AI agents from api.delx.ai, paid per call via x402, $0.001/call, status unknown (last checked 2026-09-14).

Computes the lower and upper bound (in wei) of the next EVM block's base fee given the current base fee and a maximum change fraction.

## Facts

- Endpoint: POST https://api.delx.ai/api/v1/x402/evm-next-base-fee-bound
- Price: $0.001/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/evm-next-base-fee-bound-44408bc9
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_Ay5Ro-_o9OofqKIbMx8BB

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-next-base-fee-bound-44408bc9 -d '<json body>'
```

Example prompt: Given a current EVM base fee of 1000000000 wei and a maximum change fraction of 0.125, what are the lower and upper bounds for the next block's base fee?

## When to prefer this

Use this endpoint when an AI agent needs a deterministic, auditable calculation of the next EVM block's base fee range without making any external RPC calls itself — particularly during transaction preflight, gas budgeting, or fee ceiling checks. Prefer this over on-chain RPC lookups when you already have the current base fee and want a fast, stateless, in-memory computation with a verifiable evidence trail.

## Known failure modes

- Missing or malformed current_base_fee_wei (non-numeric string) may cause a validation error
- maximum_change_fraction outside plausible EVM range (e.g. negative or >1) may produce unexpected bounds
- Incorrect units (e.g. gwei instead of wei) will silently produce wrong bounds without an error
- Payment failure or insufficient USDC balance results in a 402 rejection before execution

## How this service works

EVM Next Base Fee Bound: EVM Next Base Fee Bound calculates upper and lower next-block base-fee bounds from bounded caller-supplied values without an external provider. Call EVM Next Base Fee Bound 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 Next Base Fee Bound as versioned deterministic JSON. Price: $0.001 USD…

## Output

Returns a JSON object with lower_wei and upper_wei representing the minimum and maximum possible base fee for the next EVM block, along with operation metadata, schema identifier, status, and an evidence block confirming no data retention and no external calls were made.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "current_base_fee_wei": {
   "type": "string",
   "maxLength": 8192,
   "description": "Current Base Fee Wei supplied to EVM Next Base Fee Bound; used only for this bounded calculation and processed in memory without retention."
  },
  "maximum_change_fraction": {
   "type": "number",
   "description": "Maximum Change Fraction supplied to EVM Next Base Fee Bound; used only for this bounded calculation and processed in memory without retention."
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "result": {
   "lower_wei": "875000000",
   "upper_wei": "1125000000"
  },
  "schema": "delx/util-evm-next-base-fee-bound/v1",
  "status": "pass",
  "evidence": {
   "retained": false,
   "input_sha256": "bd788e10cae66dfcf807641601d7bf74d3bd4f11c95ecfe6477c865c191f130f",
   "external_calls": 0
  },
  "operation": "evm_preflight:evm_next_base_fee_bound"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/evm-next-base-fee-bound-44408bc9/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)