# Accelerometer Delta — AI-Progress Series Comparison

> Accelerometer Delta — AI-Progress Series Comparison 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 2026-09-19).

Returns the absolute and percentage change between two dated snapshots across 129 AI-progress and technology time series, showing per-source from/to values and whether new observations landed

## Facts

- Endpoint: GET https://x402-accelerometer-feed.fly.dev/delta/:from/:to
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-19
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/accelerometer-delta-ai-progress-series-comparison-b641b2b3
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_ePWHCBg8oYx3zZ-C468aa

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-delta-ai-progress-series-comparison-b641b2b3
```

Example prompt: Show me what changed across all 129 AI-progress and technology series between the 2024-06-01 and 2024-12-01 Accelerometer snapshots — I want to see the absolute and percentage deltas per source and which series got new observations.

## When to prefer this

Use this endpoint when you need to quantify how AI-progress metrics, benchmark scores, compute trends, model pricing, or related technology series have shifted between two specific points in time. It is the right choice when you want per-source breakdowns with both absolute and percentage changes and a flag for newly landed observations. Prefer it over the latest-snapshot or single-snapshot endpoints when your goal is comparative analysis or trend measurement across a time window rather than a point-in-time reading.

## Known failure modes

- Invalid or non-existent snapshot date IDs return an error or empty result — valid IDs must be obtained from the free menu at /
- 'from' date later than 'to' date may return zero or negative deltas without an explicit error
- Payment not included or insufficient (requires $0.01 USDC via x402 protocol) results in a 402 Payment Required response
- Network timeout if the fly.dev instance is cold-starting
- Missing path parameters (:from or :to) result in a routing error

## How this service works

What changed between two dated snapshots of 129 AI-progress and technology series: per source the from/to values and dates, absolute and % change, and whether a new observation landed. Covers frontier benchmark scores, compute trends, AGI prediction-market odds, model pricing, AI stocks and crypto, energy, space, robotics, research output. Ids are YYYY-MM-DD from the free menu at /. No composite score.

## Output

A JSON object of kind 'delta' containing: the from and to snapshot identifiers, n_sources (129), n_moved (count of series with a newer observation in the 'to' snapshot), and a 'sources' array where each element includes the series id, domain, metric, unit, from object (value + date), to object (value + date), delta_abs, delta_pct, and a new_observation boolean. The composite field is always null.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "pathParams": {
     "type": "object",
     "required": [
      "from",
      "to"
     ],
     "properties": {
      "to": {
       "type": "string",
       "description": "later reading id"
      },
      "from": {
       "type": "string",
       "description": "earlier reading id"
      }
     }
    },
    "queryParams": {
     "type": "object",
     "properties": {}
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "required": [
      "kind",
      "from",
      "to",
      "sources"
     ],
     "properties": {
      "to": {
       "type": "object"
      },
      "from": {
       "type": "object"
      },
      "kind": {
       "type": "string",
       "const": "delta"
      },
      "n_moved": {
       "type": "integer",
       "description": "sources with a newer observation in `to`"
      },
      "sources": {
       "type": "array",
       "items": {
        "type": "object",
        "properties": {
         "id": {
          "type": "string"
         },
         "to": {
          "type": "object"
         },
         "from": {
          "type": [
           "object",
           "null"
          ]
         },
         "unit": {
          "type": "string"
         },
         "domain": {
          "type": "string"
         },
         "metric": {
          "type": "string"
         },
         "delta_abs": {
          "type": [
           "number",
           "null"
          ]
         },
         "delta_pct": {
          "type": [
           "number",
           "null"
          ]
         },
         "new_observation": {
          "type": "boolean"
         }
        }
       }
      },
      "composite": {
       "type": "null"
      },
      "n_sources": {
       "type": "integer"
      }
     }
    }
   }
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/accelerometer-delta-ai-progress-series-comparison-b641b2b3/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)