# Accelerometer AI-Progress Delta Feed (x402)

> Accelerometer AI-Progress Delta Feed (x402) is a paid API for AI agents from x402-accelerometer-feed.fly.dev, paid per call via x402, $0.01/call, status unknown (last checked 2026-09-18).

Returns the change (delta) in 129 AI-progress and technology time series between two specified dates, paid via USDC on Base using x402.

## Facts

- Endpoint: GET https://x402-accelerometer-feed.fly.dev/ai-progress/what-changed/%7Bfrom%7D/%7Bto%7D
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-18
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/accelerometer-ai-progress-delta-feed-x402-0c819a16
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_R6Xs56xE4uhnyxsXPiqSc

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 accelerometer-ai-progress-delta-feed-x402-0c819a16
```

Example prompt: Show me everything that changed in AI progress metrics between July 12 2026 and September 16 2026 — I want the deltas across all 129 series including benchmarks, compute, AGI prediction-market odds, and model pricing.

## When to prefer this

Choose this endpoint when you need to measure how much AI-progress metrics have changed between two specific dates rather than just viewing the current or historical state. It is the right choice for acceleration analysis, trend velocity measurement, and identifying which of the 129 tracked series moved the most over a given window. Prefer it over the snapshot endpoints when the question is 'what changed?' rather than 'what is the current value?'

## Known failure modes

- Invalid or malformed date strings in {from} or {to} path parameters return an error
- Date outside available snapshot range returns no data or an empty delta
- Payment failure or insufficient USDC balance on Base results in 402 payment required response
- Network timeout from the fly.dev host may occur under load
- Snapshot not yet generated for a future date returns an error or empty result

## How this service works

Readings of AI progress: dated snapshots of 129 public AI-progress and technology time series (frontier benchmark scores, compute trends, AGI prediction-market odds, model pricing, AI stocks and crypto, energy, space, robotics, biomed, research output), and the acceleration between any two readings. Paid with USDC on Base via x402.

## Output

A JSON object containing the two snapshot timestamps (from/to), the kind field set to 'delta', the number of series that moved (n_moved), and an array of per-source entries each with absolute and percentage delta values, unit, domain label, metric name, and a new_observation flag. Also includes total n_sources (129) and schema version.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "properties": {
   "type": "string"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "to": {
   "run_at": "2026-09-16T12:25:28.530204+00:00",
   "snapshot_id": "2026-09-16"
  },
  "from": {
   "run_at": "2026-07-12T14:00:05.754191+00:00",
   "snapshot_id": "2026-07-12"
  },
  "kind": "delta",
  "n_moved": 76,
  "sources": [
   {
    "id": "agents.x402_services_count",
    "to": {
     "date": "2026-09-16",
     "value": 2865
    },
    "from": {
     "date": "2026-07-12",
     "value": 1779
    },
    "unit": "count",
    "domain": "agents",
    "metric": "x402 pay-per-request services (agentic.market)",
    "delta_abs": 1086,
    "delta_pct": 61.0455,
    "new_observation": true
   },
   {
    "id": "autonomy.metr_time_horizon_50",
    "to": {
     "date": "2025-04-16",
     "value": 112.230447
    },
    "from": {
     "date": "2025-04-16",
     "value": 112.230447
    },
    "unit": "minutes",
    "domain": "autonomy",
    "metric": "METR frontier task-completion horizon @50% (minutes)",
    "delta_abs": 0,
    "delta_pct": 0,
    "new_observation": false
   }
  ],
  "composite": null,
  "n_sources": 129,
  "schema_version": "0.2"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/accelerometer-ai-progress-delta-feed-x402-0c819a16/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from x402-accelerometer-feed.fly.dev](https://www.zero.xyz/host/x402-accelerometer-feed.fly.dev/llms.txt)