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Agent402 UK — Budget Preflight Check
x402
Agent402 UK — Budget Preflight Check is a paid API for AI agents from agent402.co.uk, paid per call via x402, $0.001/call, status unknown (last checked 2026-09-14).
Checks whether a planned LLM call fits within a specified USD budget ceiling before executing, returning an allow/deny decision with estimated cost and headroom
Price / call$0.001
Success—
StatusUnknown
How this service works
Don't burn tokens on deterministic work. Go/no-go jobs first: payout preflight, text firewall (PII/secrets), budget check — then rails, calendars, finmath. x402 USDC on Base. UK + global. agent402.co.uk — not agent402.tools. $0.001–$0.002 USDC on Base. No API keys.
Output
Returns a JSON object with: `allow` (boolean go/no-go), `valid` (boolean), `estimated_usd` (computed cost for the call), and `headroom_usd` (budget ceiling minus estimated cost). Allows the agent to gate execution before spending tokens.
Example use cases
Guard expensive multi-step agent turn
“I'm about to run a 5,000-token prompt through GPT-4o three times — check whether that fits under my $0.20 hard limit before I fire it off, and show me the estimated cost and remaining headroom.”
Per-call budget validation for cost-capped product
“My app has a $0.01 per-user-turn limit on cl100k_base. Before I process this user's message, verify that the 800-token prompt won't exceed that ceiling.”
Preflight check before batch LLM scoring job
“I need to score 50 documents using GPT-4o with roughly 400 tokens each — can you check upfront whether the total cost stays under $0.15, and tell me the estimated spend?”
Technical details
Endpoint
POSThttps://agent402.co.uk/v1/jobs/budget-preflightWhen to prefer
Choose this endpoint when you need a cheap ($0.001), deterministic, pre-execution gate to avoid overspending on LLM calls — especially in multi-turn agents, cost-capped products, or batch jobs. Prefer it over post-hoc cost tracking because it prevents spend rather than reporting it. Better than computing token costs in-agent because it offloads deterministic arithmetic and keeps the decision auditable without burning agent context.
Side effects
- Missing both `text` and `input_tokens` — cannot estimate cost without one or the other
- Unknown or unsupported model name — may return an error or fall back to a default rate
- max_usd not provided — budget comparison cannot be performed
- Negative or zero calls factor — invalid repeat multiplier
- Payment failure via x402 — call blocked if USDC payment on Base is not completed
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| text | string | Prompt / context to count (optional if input_tokens set) |
| calls | number | Repeat factor, default 1 |
| model | string | gpt-4o | cl100k_base | … |
| max_usd | number | Hard ceiling for this turn |
| input_tokens | number | Skip counting if you already know |
| output_tokens | number | Optional; default 25% of input |
Output
Schema · Response
{
"type": "json",
"example": {
"allow": true,
"valid": true,
"headroom_usd": 0.0479,
"estimated_usd": 0.0021
}
}Tags
x402
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