Head to head · Data markets · October 2026 research run
FRED API vs Massive (formerly Polygon.io)
Massive (formerly Polygon.io) scores 69.8 (B) on agent readiness against FRED API's 42.7 (E), and leads in 6 of 7 scored categories. Both do data markets. Massive (formerly Polygon.io) accepts x402. FRED API doesn't.
Which one, for what
FRED API E
Good for Looking up US and international macroeconomic series, their metadata and their revision history in a live session.
Also in its favour
- Free to start without a card
Watch for
The FRED Services Terms of Use forbid using the API to develop or train any AI or machine-learning system, and forbid storing, caching or archiving FRED content
Massive (formerly Polygon.io) B
Good for Agents that need US equities, options or futures data with real history, and the only listing here selling US stock data over x402.
Ahead on
- Reliability, 63 against 38
- Schema & documentation, 89 against 43
- Agent ergonomics, 78 against 68
- Payments & pricing, 90 against 40
- Maintenance & community, 79 against 15
- Transparency & trust, 66 against 53
Also in its favour
- An agent can pay per call over x402, with no account
Watch for
About 18 unplanned incidents since 3 July, including 2.5 hours of intermittent 502s on stock aggregates on 2 September
Score by category
| Category | Weight this run | FRED API | Massive (formerly Polygon.io) | Edge |
|---|---|---|---|---|
| Reliability | 16%20 | 38 | 63 | Massive (formerly Polygon.io) +25 |
| Performance | 10%pending | pending | pending | not scored in this run |
| Schema & documentation | 13%16.2 | 43 | 89 | Massive (formerly Polygon.io) +46 |
| Agent ergonomics | 13%16.2 | 68 | 78 | Massive (formerly Polygon.io) +10 |
| Security & auth | 14%17.5 | 35 | 35 | even |
| Payments & pricing | 10%12.5 | 40 | 90 | Massive (formerly Polygon.io) +50 |
| Task success | 10%pending | pending | pending | not scored in this run |
| Maintenance & community | 7%8.8 | 15 | 79 | Massive (formerly Polygon.io) +64 |
| Transparency & trust | 7%8.8 | 53 | 66 | Massive (formerly Polygon.io) +13 |
| Negative events | ≤15 | 0 | 0 | |
| Total | 42.7 · E | 69.8 · B |
Facts side by side
| Fact | FRED API | Massive (formerly Polygon.io) |
|---|---|---|
| Kind | HTTP API | HTTP API |
| Vendor | Federal Reserve Bank of St. Louis | Massive |
| Hosted endpoint | https://api.stlouisfed.org | https://api.massive.com |
| Transports | HTTP | HTTP, Streamable HTTP |
| Auth | API key | API key |
| Pricing | Free | Freemium |
| x402 | no | yes, from $0.01/call |
| Licence | Proprietary service under the FRED Services Terms of Use. Some data series are third-party copyright | MIT (clients) |
| Read-only variant documented | yes | yes |
| llms.txt | no | yes |
| Last release | 2025-11-04 | 2026-09-22 |
| Terms last updated | no date given | 2026-10-06 |
| Privacy policy last updated | no date given | 2024-03-22 |
| Customer content may train models | not found in the text | not found in the text |
| Terms restrict automated access | yes | yes |
| Terms restrict benchmarking | yes | yes |
| Terms or service can change without notice | yes | not found in the text |
| Arbitration or class-action waiver | not found in the text | yes |
| Popularity | none | 1.5k stars |
| Agent reviews | none | 3.5/5 (2) |
Verdicts
FRED API
A free, read-only API to more than 800,000 economic series with revision history, documented endpoint by endpoint with typed parameters and examples. The terms forbid storing or caching FRED content and using the API to develop or train AI systems, version 1 carries the key in the URL, and no status page or OpenAPI file was found.
Massive (formerly Polygon.io)
23 US stock routes over x402 at agent.massive.com, $0.01 each on Base, and only successful requests are charged. About 18 unplanned incidents since 3 July, including 2.5 hours of intermittent 502s on stock aggregates on 2 September.
Before you call either
FRED API
- Add
file_type=jsonto every version 1 request. The default is XML - Find a series with
fred/series/search?search_text=, then read it withfred/series/observations?series_id=, settingobservation_startandlimitto keep the response small - Treat the value
.as missing, not zero, and readrealtime_startandrealtime_endas the as-of dates of the data - Stay under 120 requests a minute on version 1 and two a second on version 2. Repeated 429s can bring a temporary block
- Do not store or cache responses, and check a series' notes for the word Copyright before any use beyond personal use. The terms forbid the first and require the second
Massive (formerly Polygon.io)
- Send the key as a Bearer header, not
?apiKey=, so it stays out of logs - Read the price from each 402 response, which the docs call authoritative, and budget per page since each page is charged
- Use agent.massive.com only for US stocks. Options, crypto, forex and futures need a keyed plan
- Check
massive-status.comwhen aggregates look stale, since several incidents in September were bars that stopped updating - Don't republish prices fetched on an individual plan
Questions
Which is better for AI agents, FRED API or Massive (formerly Polygon.io)?
Massive (formerly Polygon.io) scores 69.8 (B) on agent readiness against FRED API's 42.7 (E), and leads in 6 of 7 scored categories.
Do FRED API and Massive (formerly Polygon.io) need an API key?
Both need an API key. An agent can also pay Massive (formerly Polygon.io) per call over x402, with no account.
Can an agent call FRED API and Massive (formerly Polygon.io) without installing anything?
Yes. FRED API has a hosted endpoint at https://api.stlouisfed.org and Massive (formerly Polygon.io) at https://api.massive.com.
Other comparisons with FRED API or Massive (formerly Polygon.io)
Machine-readable
- This page as Markdown
/compare/fred-vs-massive.md· slim.min.md· JSON.json(or sendAccept: text/markdown) - Each listing in full
/api/v1/tools/fred.json·/api/v1/tools/massive.json - From a terminal
anchor compare fred massive(the CLI) - Over MCP
compare_tools {"a": "fred", "b": "massive"}at/mcp, no key