# Fathom Macroeconomic Data API — Compare Series

> Fathom Macroeconomic Data API — Compare Series is a paid API for AI agents from fathom-opal.vercel.app, paid per call via x402, $0.15/call, status unknown (last checked 2026-09-14).

Compares 2–5 FRED economic time series side-by-side, returning aligned observations for cross-series analysis

## Facts

- Endpoint: POST https://fathom-opal.vercel.app/api/compare
- Price: $0.15/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/fathom-macroeconomic-data-api-compare-series-9363b374
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_JpPP4ZJ0OjyL688yWqUeo

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 fathom-macroeconomic-data-api-compare-series-9363b374 -d '<json body>'
```

Example prompt: Pull the last 20 observations for US GDP (GDPC1), CPI inflation (CPIAUCSL), and the unemployment rate (UNRATE) from FRED and show me how they compare side by side.

## When to prefer this

Use this endpoint when you need to compare multiple macroeconomic time series simultaneously and already know the FRED series IDs. It is ideal for correlation analysis, charting economic trends across indicators, or building dashboards that juxtapose GDP, inflation, unemployment, or interest rate data. Prefer this over single-series endpoints when the user's question involves relationships between two or more indicators.

## Known failure modes

- Invalid FRED series ID returns an error or empty data for that series
- Fewer than 2 or more than 5 series IDs provided may return a validation error
- Series with different frequencies (e.g. monthly vs quarterly) may not align cleanly
- Rate limiting or upstream FRED API unavailability causes 5xx errors
- Invalid limit parameter (non-numeric or out-of-range) may cause unexpected behavior

## How this service works

Free macroeconomic data API powered by FRED. 816,000+ economic time series. GDP, inflation, unemployment, interest rates, and more.

## Output

Returns a structured comparison object containing aligned time series observations for each requested FRED series ID, along with a source attribution string identifying FRED as the data provider. The comparison object maps each series ID to its observations, enabling side-by-side analysis of up to 5 macroeconomic indicators.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "required": [
  "seriesIds"
 ],
 "properties": {
  "limit": {
   "type": "string",
   "description": "Observations per series (default: 10)"
  },
  "seriesIds": {
   "type": "array",
   "description": "Array of 2-5 FRED series IDs to compare"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "object",
 "required": [
  "source"
 ],
 "properties": {
  "source": {
   "type": "string"
  },
  "comparison": {
   "type": "object"
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/fathom-macroeconomic-data-api-compare-series-9363b374/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from fathom-opal.vercel.app](https://www.zero.xyz/host/fathom-opal.vercel.app/llms.txt)