# Delx Seeded Holdout Assignment

> Delx Seeded Holdout Assignment 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).

Deterministically assigns a subject to a treatment or holdout group using a seed, returning a stable group label and bucket value based on a configurable holdout fraction.

## Facts

- Endpoint: POST https://api.delx.ai/api/v1/x402/seeded-holdout-assignment
- 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/delx-seeded-holdout-assignment-c1b7fe84
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_zpwyexopAEhFEls0CHFLe

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 delx-seeded-holdout-assignment-c1b7fe84 -d '<json body>'
```

Example prompt: Assign user ID 'user_98234' to either the treatment or holdout group using seed 'exp_launch_v2' with a 20% holdout fraction, and tell me which group they land in.

## When to prefer this

Use this endpoint when you need a stateless, reproducible, privacy-safe way to assign subjects to holdout vs. treatment groups without storing assignment state. Ideal for agent workflows that must make consistent branching decisions across calls using only a seed and subject identifier. Prefer this over random assignment when repeatability matters, and over stateful systems when you want zero data retention guarantees.

## Known failure modes

- Missing required fields (seed, subject, holdout_fraction) result in a validation error
- holdout_fraction outside the 0–1 range may cause unexpected behavior or an error
- Overly long seed or subject strings (beyond 8192 chars) will be rejected
- Payment failure via x402 protocol will prevent the call from being processed

## How this service works

Seeded Holdout Assignment: Seeded Holdout Assignment assigns a stable subject to holdout or treatment from bounded caller-supplied values without an external provider. Call Seeded Holdout Assignment when an agent needs a reproducible decision that another run can independently replay. Returns the deterministic selection plus seed provenance, population bounds, and the operation-specific outcome for Seeded Holdout Assignment as versioned deterministic JSON. Price: $0.001 USDC via x402 on Base. F…

## Output

Returns a JSON object with a 'group' field ('treatment' or 'holdout'), a numeric 'bucket' value (0–1) reflecting the deterministic hash position, the schema version, a 'status' of 'pass', and evidence metadata including whether data was retained (always false), the SHA-256 of the input, and the number of external calls made (always 0).

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "seed": {
   "type": "string",
   "maxLength": 8192,
   "description": "Seed supplied to Seeded Holdout Assignment; used only for this bounded calculation and processed in memory without retention."
  },
  "subject": {
   "type": "string",
   "maxLength": 8192,
   "description": "Subject supplied to Seeded Holdout Assignment; used only for this bounded calculation and processed in memory without retention."
  },
  "holdout_fraction": {
   "type": "number",
   "description": "Holdout Fraction supplied to Seeded Holdout Assignment; used only for this bounded calculation and processed in memory without retention."
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "result": {
   "group": "treatment",
   "bucket": 0.5223946972379113
  },
  "schema": "delx/util-seeded-holdout-assignment/v1",
  "status": "pass",
  "evidence": {
   "retained": false,
   "input_sha256": "bd5b582a9597f6cff6a8c3ed859bd7cf28c6eac4c434b4828c22df3b23d6e4ef",
   "external_calls": 0
  },
  "operation": "seeded_decision:seeded_holdout_assignment"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/delx-seeded-holdout-assignment-c1b7fe84/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)