# d21 signal_delta

> d21 signal_delta is a paid API for AI agents from draconic21-x402-api.onrender.com, paid per call via x402, $0.05/call, status unknown (last checked 2026-10-27).

Returns a complete diff of the Daily Agent Signal since a specified date — all added, changed (with before/after field values), and removed records — against a stored archive baseline.

## Facts

- Endpoint: POST https://draconic21-x402-api.onrender.com/v1/signal_delta?utm_source=zero.xyz
- Price: $0.05/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-27
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/d21-signal-delta-7425103b
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap__8mlPWuTy5qsGt9o_FDbt

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 d21-signal-delta-7425103b -d '<json body>'
```

Example prompt: Pull me the full signal delta from the Daily Agent Signal since 2025-06-10 — I need to see everything that was added, removed, or changed with before-and-after values.

## When to prefer this

Use this endpoint when you need a precise, field-level diff of the Daily Agent Signal since a known date — especially for incremental sync, change monitoring, or audit use cases. Prefer this over re-fetching the full signal snapshot when you already have a stored baseline date and want only what changed. Use /v1/signal_delta/availability first to confirm a baseline exists before paying.

## Known failure modes

- 422 Unprocessable Entity if no stored baseline exists for the provided since_date (check /v1/signal_delta/availability?since_date= first, free of charge)
- Invalid date format (must be YYYY-MM-DD) returns a validation error
- Date too recent or too old may yield empty or unavailable baseline
- Payment failure (x402) blocks access to the paid endpoint

## How this service works

GO-TO PRODUCT: what changed in the Daily Agent Signal since a date you read: complete added, changed (fields plus before/after) and removed records, diffed against our stored archive. Body { since_date }. Free first: /v1/signal_delta/availability?since_date= (absent baseline is 422, no charge) and /v1/signal_delta/example.

## Output

A structured diff object containing three categories: added records (new entries since the baseline date), changed records (modified entries with per-field before/after values), and removed records (entries no longer present) — all compared against the stored archive for the given since_date.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "since_date": {
   "type": "string",
   "format": "date",
   "description": "Stored baseline date in YYYY-MM-DD format; check free availability first."
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/d21-signal-delta-7425103b/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from draconic21-x402-api.onrender.com](https://www.zero.xyz/host/draconic21-x402-api.onrender.com/llms.txt)