# Subscription Spend Guard

> Subscription Spend Guard is a paid API for AI agents from phion.systems, paid per call via x402, $0.003/call, status unknown (last checked 2026-09-14).

Enforces recurring period budgets for agent subscriptions, blocking spend that exceeds defined limits within a billing cycle

## Facts

- Endpoint: POST https://phion.systems/v1/paid/trust/subscription-spend-guard
- Price: $0.003/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/subscription-spend-guard-b9bc9b0a
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_A4CkAp2B1KrtD6XsaG_fT

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 subscription-spend-guard-b9bc9b0a -d '<json body>'
```

Example prompt: Before processing this subscription renewal, check if it would exceed my $50 monthly budget cap for recurring services — the current spend this period is $43.20 and this charge is $9.99.

## When to prefer this

Use this endpoint when an AI agent needs to enforce hard budget caps on recurring or subscription-based spending within defined billing periods. It is specifically designed for periodic/recurring cost governance rather than one-off transaction limits. Prefer this over generic payment validation when the use case involves subscription renewals, repeating charges, or cycle-based budget tracking.

## Known failure modes

- Missing or malformed budget limit causes validation failure
- Period definition not recognized or missing results in inability to evaluate budget window
- Spend amount exceeds budget — returns rejection with overage details
- Invalid currency or currency mismatch causes processing error
- Ambiguous period boundaries (e.g. overlapping cycles) may cause indeterminate result

## How this service works

Enforce recurring period budgets

## Output

Returns an enforcement decision indicating whether the recurring spend is approved or rejected, along with the remaining budget allowance for the current period, the current cumulative spend, the period reset time, and any policy rule that triggered a rejection.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema"
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/subscription-spend-guard-b9bc9b0a/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from phion.systems](https://www.zero.xyz/host/phion.systems/llms.txt)