# Fathom Macroeconomic Data API — Category Series Lookup

> Fathom Macroeconomic Data API — Category Series Lookup is a paid API for AI agents from fathom-opal.vercel.app, paid per call via x402, $0.06/call, status unknown (last checked 2026-09-14).

Returns a list of FRED economic time series belonging to a specified category, such as GDP, inflation, or unemployment indicators.

## Facts

- Endpoint: POST https://fathom-opal.vercel.app/api/category-series
- Price: $0.06/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-category-series-lookup-97711b00
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_Ib8K4qH5dK9sKVHe5EzuS

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-category-series-lookup-97711b00 -d '<json body>'
```

Example prompt: Can you pull up all the economic time series available under FRED category 32455 — I want to see what inflation-related data series are in there, show me up to 30 results.

## When to prefer this

Use this endpoint when you need to discover or enumerate what time series exist within a known FRED category, rather than fetching actual data values. Ideal for building category browsers, populating series selection menus, or exploring what macroeconomic indicators are available before committing to a specific series. Prefer this over a general FRED search when you already know the category ID and want a structured list of its series.

## Known failure modes

- Invalid or non-existent categoryId returns an empty series array or error
- Missing required categoryId field causes a validation error
- Limit parameter out of expected range may be ignored or cause an error
- FRED upstream unavailability results in failed data retrieval
- Very large categories may return truncated results if limit is not specified

## How this service works

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

## Output

An array of FRED time series objects belonging to the requested category, each containing series metadata (likely series ID, title, units, frequency, and other descriptors), along with the source attribution string and the category ID that was queried.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "required": [
  "categoryId"
 ],
 "properties": {
  "limit": {
   "type": "string",
   "description": "Max results (default: 20)"
  },
  "categoryId": {
   "type": "string",
   "description": "FRED category ID"
  }
 }
}
```

## Response schema (JSON Schema)

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

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/fathom-macroeconomic-data-api-category-series-lookup-97711b00/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)