# Agent Delivery Fallback Gate

> Agent Delivery Fallback Gate 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).

Validates whether a declared fallback is permissible given failure conditions and caller-supplied challenge/result metadata before accepting or paying for an x402 agent delivery.

## Facts

- Endpoint: POST https://api.delx.ai/api/v1/x402/agent-delivery-fallback-gate
- 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/agent-delivery-fallback-gate-3fb39106
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_pVBLDnfkdm7lW5gulpyA7

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 agent-delivery-fallback-gate-3fb39106 -d '<json body>'
```

Example prompt: Before I accept and pay for this agent delivery fallback, check if the failure code 'TIMEOUT_503' with primary status 'partial' is allowed to fall back — the allowed codes are ['TIMEOUT_503', 'RATE_LIMIT_429'] and fallback_available is true.

## When to prefer this

Use this endpoint when you need to gate acceptance or payment of an x402 agent delivery that includes a fallback claim, especially when you want to verify that the failure conditions genuinely permit a fallback before committing funds. Prefer this over manual logic when dealing with complex allowed-code lists or when audit-quality normalized evidence and explicit accept/reject outputs are required.

## Known failure modes

- Missing or malformed failure_code causes validation to fail with unclear rejection
- fallback_available set incorrectly may lead to unexpected rejection despite valid codes
- Caller-supplied allowed_failure_codes list not matching contract expectations causes false rejections
- Empty allowed_failure_codes array results in blanket rejection of all fallbacks
- Primary status not aligning with failure_code produces mismatch reasons even for valid scenarios

## How this service works

Agent Delivery Fallback Gate: Agent Delivery Fallback Gate checks whether failure conditions permit a declared fallback from bounded caller-supplied values without an external provider. Call Agent Delivery Fallback Gate before paying for or accepting an x402 or agent delivery assembled from caller-supplied challenge and result metadata. Returns contract-specific checks, normalized evidence, mismatch reasons, and an explicit acceptance or rejection status for Agent Delivery Fallback Gate as vers…

## Output

Returns contract-specific validation checks, normalized evidence of the failure conditions, reasons for any mismatch between declared and allowed fallback codes, and an explicit acceptance or rejection status indicating whether the fallback claim should be honored.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "failure_code": {
   "type": "string",
   "maxLength": 8192,
   "description": "Failure Code supplied to Agent Delivery Fallback Gate; used only for this bounded calculation and processed in memory without retention."
  },
  "primary_status": {
   "type": "string",
   "maxLength": 8192,
   "description": "Primary Status supplied to Agent Delivery Fallback Gate; used only for this bounded calculation and processed in memory without retention."
  },
  "fallback_available": {
   "type": "boolean",
   "description": "Fallback Available supplied to Agent Delivery Fallback Gate; used only for this bounded calculation and processed in memory without retention."
  },
  "allowed_failure_codes": {
   "type": "array",
   "items": {
    "type": "string",
    "maxLength": 8192
   },
   "maxItems": 256,
   "description": "Allowed Failure Codes supplied to Agent Delivery Fallback Gate; used only for this bounded calculation and processed in memory without retention."
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "result": {
   "failure_allowed": true,
   "fallback_permitted": true
  },
  "schema": "delx/util-agent-delivery-fallback-gate/v1",
  "status": "pass",
  "evidence": {
   "retained": false,
   "input_sha256": "90bc182d30b20aad9cdbf98c44d1452bf8205f8ad59c3d598c333e1fd05badaf",
   "external_calls": 0
  },
  "operation": "delivery_contract:agent_delivery_fallback_gate"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/agent-delivery-fallback-gate-3fb39106/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)