# Fathom Macroeconomic Data API — Related Series Lookup

> Fathom Macroeconomic Data API — Related Series Lookup is a paid API for AI agents from fathom-opal.vercel.app, paid per call via x402, $0.04/call, status unknown (last checked 2026-09-14).

Returns related FRED economic time series and their categories for a given series ID

## Facts

- Endpoint: POST https://fathom-opal.vercel.app/api/related
- Price: $0.04/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-related-series-lookup-0e4f16ec
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_ZYR22Gm_LhmG4PkcbNQ3Z

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-related-series-lookup-0e4f16ec -d '<json body>'
```

Example prompt: Can you find all the FRED economic series related to the US unemployment rate series UNRATE and show me what categories they belong to?

## When to prefer this

Use this endpoint when you need to discover economic time series that are related to a known FRED series ID — ideal for expanding economic research, building dashboards, or exploring the FRED taxonomy around a specific indicator. Prefer this over a general FRED series search when you already have a specific series ID and want to find its neighbors or category context.

## Known failure modes

- Invalid or nonexistent FRED series ID returns empty or error response
- Missing required seriesId field returns validation error
- Downstream FRED API unavailability causes service failure
- Payment not provided or insufficient USDC results in x402 payment required error

## 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 JSON object containing the source (FRED), the queried series ID, and an array of related series objects with their category metadata, enabling discovery of contextually connected economic time series.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "required": [
  "seriesId"
 ],
 "properties": {
  "seriesId": {
   "type": "string",
   "description": "FRED series ID"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "object",
 "required": [
  "source"
 ],
 "properties": {
  "source": {
   "type": "string"
  },
  "series_id": {
   "type": "string"
  },
  "categories": {
   "type": "array",
   "items": {
    "type": "object"
   }
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/fathom-macroeconomic-data-api-related-series-lookup-0e4f16ec/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)