Developer API

REST API reference for querying 2.9M Form 5500 filings

Overview

55 Hundred provides a REST API for querying 2.9M+ Form 5500 filings spanning 2022–2025. Data includes plan financials, participant counts, asset values, recordkeeper identification, and compliance flags derived from DOL public data.

All API responses are JSON. Errors return an object with an error key.

Authentication

Pass your API key in the x-api-key request header. Get your key from the Account page.

curl -H "x-api-key: YOUR_API_KEY" \
  "https://55-hundred.app/api/search?q=Acme+Corp"

Requests without a valid API key return 401 Unauthorized.

Base URL

All endpoints are relative to:

https://55-hundred.app

Search Plans

GET/api/search

Full-text search across plan names and company names, with filters for state, assets, participants, and more. Returns up to 200 results per page.

Parameter	Type	Required	Description
`q`	string	No	Company name or EIN to search
`state`	string	No	Two-letter state code (e.g. CA, NY)
`plan_type`	string	No	Filter by plan type. Default: "401k"
`min_assets`	number	No	Minimum total assets in USD
`max_assets`	number	No	Maximum total assets in USD
`min_parts`	number	No	Minimum participant count
`max_parts`	number	No	Maximum participant count
`sort_by`	string	No	Sort field: "assets", "participants", "growth", "name"
`sort_dir`	string	No	"asc" or "desc" (default: desc)
`year`	number	No	Form year filter (2022–2025)
`limit`	number	No	Results per page. Max 200. Default 50.
`offset`	number	No	Pagination offset. Default 0.

Example request

curl -H "x-api-key: YOUR_API_KEY" \
  "https://55-hundred.app/api/search?q=Starbucks&state=WA&min_assets=10000000&limit=10"

Example response

{
  "results": [
    {
      "ein": "911587655",
      "name": "STARBUCKS CORPORATION",
      "plan_name": "STARBUCKS CORPORATION 401(K) PLAN",
      "state": "WA",
      "city": "SEATTLE",
      "assets": 2847000000,
      "employees": 298000,
      "recordkeeper": "Fidelity",
      "asset_growth_pct": 4.2,
      "form_year": 2024,
      "compliance_flags": []
    }
  ],
  "total": 1
}

Company Lookup

GET/api/company

Look up a specific company by EIN. Returns the most recent filing plus historical data.

Parameter	Type	Required	Description
`ein`	string	Yes	9-digit EIN (with or without hyphen)

Example request

curl -H "x-api-key: YOUR_API_KEY" \
  "https://55-hundred.app/api/company?ein=91-1587655"

Example response

{
  "company": {
    "ein": "911587655",
    "name": "STARBUCKS CORPORATION",
    "latest": {
      "form_year": 2024,
      "assets": 2847000000,
      "employees": 298000,
      "recordkeeper": "Fidelity"
    },
    "history": [
      { "form_year": 2023, "assets": 2732000000, "employees": 287000 },
      { "form_year": 2022, "assets": 2614000000, "employees": 274000 }
    ]
  }
}

Rate Limits

The API enforces a limit of 60 requests per minute per IP address. Exceeding this limit returns 429 Too Many Requests.

Rate limit headers

The API does not currently return rate limit headers. If you need higher throughput for batch enrichment, contact the 55 Hundred team.