# Financial Datasets vs Massive (formerly Polygon.io)

> Massive scores 73.1 (BB) to Financial Datasets's 61.8 (C) for market prices. Prices, MCP, x402, uptime and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/financial-datasets-vs-massive
- Markdown: https://www.anchorterminal.com/compare/financial-datasets-vs-massive.md (~4,900 tokens)
- Site index for agents: https://www.anchorterminal.com/llms.txt (the key docs and every listing in one file, at most 16 MB, about 4 million tokens: https://www.anchorterminal.com/llms-full.txt)
- API: https://www.anchorterminal.com/api/v1/index.json
- MCP: https://www.anchorterminal.com/mcp (the whole catalogue as tools, no key)
- DNS: dig +short TXT <slug>.grade.anchorterminal.com (the grade as a DNS TXT record, for a sandbox with no HTTP where names still resolve; also top., best.<category>. and <a>.vs.<b>. under the zone, and the same under grade.letme.dev)
- Licence: CC BY 4.0, credit Anchor Terminal and link this page (https://www.anchorterminal.com/terms/#data)
- Updated: 2026-11-03

Massive (formerly Polygon.io) scores 73.1 (BB) on agent readiness against Financial Datasets's 61.8 (C), and leads in 6 of 7 scored categories. Financial Datasets leads on security & auth. Both do market prices.

- Financial Datasets: grade C, 61.8/100, rank #492 of 1349. Markdown https://www.anchorterminal.com/tools/financial-datasets.md · JSON https://www.anchorterminal.com/api/v1/tools/financial-datasets.json
- Massive (formerly Polygon.io): grade BB, 73.1/100, rank #100 of 1349. Markdown https://www.anchorterminal.com/tools/massive.md · JSON https://www.anchorterminal.com/api/v1/tools/massive.json
- Best financial market data APIs for AI agents: https://www.anchorterminal.com/best/market-data/index.md
- All 55 markets comparisons: https://www.anchorterminal.com/compare/market-data/index.md

## Which one, for what

### Financial Datasets (C)

Good for: An agent doing US company research from SEC-sourced statements, filings, insider and institutional data that wants to pay per call with no account, or a small team on credits.

Ahead on:
- Security & auth, 49 against 35

Watch for: No status page, incident history or published uptime; the Professional plan's SLA terms aren't public

### Massive (formerly Polygon.io) (BB)

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, 78 against 43
- Schema & documentation, 89 against 80
- Agent ergonomics, 78 against 73
- Payments & pricing, 90 against 75
- Maintenance & community, 82 against 56

Also in its favour:
- Agent-ready, a grade of BB or better

Watch for: 14 partial incidents from 3 August to 1 November 2026, mostly stale or missing data on stock aggregates and quotes


## Why the edge

### Reliability: Massive (formerly Polygon.io) +35

- Financial Datasets (43): Graded as a hosted service. No status page was found; status.financialdatasets.ai does not resolve and no page links one (0), so there is no incident history to read (5). The only published limit is 10,000 requests a minute per wallet over x402, with monthly request caps per plan and none per minute for keyed plans (8 of 15). The OpenAPI file declares 429 and the x402 page documents a 503 with Retry-After from the facilitator and a `duplicate_payment` check on replayed signatures (10 of 15). The Professional plan lists uptime SLAs, with no figure published (10). The API is generally available (10). Total 43.
- Massive (formerly Polygon.io) (78): Atlassian Statuspage at massive-status.com with REST, WebSocket and flat-file components for each asset class (20). The history feed lists 14 unplanned incidents from 3 August to 1 November 2026, each limited to one product, one endpoint, one asset class or some accounts. They include US equity aggregate bars missing for roughly two-thirds of US equities from 18:46 ET on 8 September until 10:29 the next day, stale stocks quotes on 20 August, and slow responses with intermittent 502s on stocks v2 aggregates from 10:37 to 13:08 ET on 2 September. The newest, on 27 October, was delayed WebSocket data and REST errors for some accounts from 13:49 to 14:17 EDT. Read the way partial incidents are read on other listings, that is minor incidents only (20). Free plan limited to 5 calls a minute, paid plans unlimited, nothing stated for x402 (10 of 15). No 429 or Retry-After guidance found in the docs or the OpenAPI file, though the official Python client retries 429 with backoff (8 of 15). The business terms dated 6 October 2026 point to a separate Support Policy and SLA document for customers who buy service levels (10). The REST API is generally available (10).

### Maintenance & community: Massive (formerly Polygon.io) +26

- Financial Datasets (56): UK fundamentals went live on 26 October 2026, India on 23 October, with Japan and South Korea dated for November on the coverage page (30). Dated changes in the last 90 days are x402 on 23 October, UK fundamentals on 26 October, terms and subprocessor list on 29 October, privacy policy on 20 August, with no changelog as such (12 of 20). Contact is a form and the dashboard; no support email, Discord or forum was found, and the GitHub organisation's four repositories couldn't be read because the GitHub API rate limit was reached (6 of 15). The PyPI package is 0.1.18 of 26 May 2024 by the founder, and the docs point to the OpenAPI file and the MCP server rather than an SDK (5 of 15). Package health unknown, dependencies not checked (3 of 10). Total 56.
- Massive (formerly Polygon.io) (82): Newest changelog entry 2026-10-28, new Insider Trading Activity and Insider Holdings endpoints (30). Changelog entries on 25 August, 1 September, 22 September, 2 October, 16 October and 28 October, six in 90 days, besides client releases (20). Public changelog and a support channel. We couldn't read GitHub issue activity in this run (10 of 15). Official clients are current, with Python v2.9.0 on 2026-10-16 and v2.9.1 on 2026-10-25, Go v3.5.0, v3.6.0 and v3.7.0 between 20 and 27 October and JavaScript v10.8.0 on 2026-09-17, each regenerated from the OpenAPI spec (15). The MCP and client repos run CI. The MCP server repository is still at v0.10.0 of 2026-05-05 and its README still calls the project experimental (7 of 10).

### Payments & pricing: Massive (formerly Polygon.io) +15

- Financial Datasets (75): x402 on the vendor's own endpoints for every documented GET data endpoint, 36 of them, with the last 365 days only and a Non-Professional licence; full history, the market snapshot, filing items and the POST endpoints need a key (35 of 40). Plan prices and overage rates are public, and each x402 endpoint quotes its price in the 402 header, $0.02 on /earnings (20). No free tier or trial found; data calls return 402 until an account holds credits, from $20 (0). An agent can pay by x402 with no account, or open an account with `POST /agent/signup` and have the owner fund it (20). Total 75.
- Massive (formerly Polygon.io) (90): x402 on its own domain at agent.massive.com since 1 September, but only 23 US stock routes. Options, indices, forex, crypto, futures, tick data and streaming still need a key (30 of 40). $0.01 a route on Agentic.Market, which the docs link to, and plan prices on massive.com/pricing, all without a login (20). Free Basic plan at 5 calls a minute with end-of-day data. The pricing page doesn't say a card is needed (20). An agent with a funded Base wallet can pay with no account (20).

### Security & auth: Financial Datasets +14

- Financial Datasets (49): A plain account key in the `X-API-KEY` header only, revoked from the dashboard, with no scopes, rotation or expiry; the MCP server adds OAuth 2 with PKCE (plain and S256), dynamic client registration, a revocation endpoint and one scope (20 of 30). Every data endpoint is a read; the x402 route and agent signup don't change the account beyond funding it (15 of 20). Filing text, filing items and news are third-party content, with no guidance on treating them as untrusted (5 of 15). The privacy policy says requests and responses are logged for up to three years; no per-call log is shown to the key holder (5 of 15). security.txt returns 404 and no bounty, SOC 2 or ISO 27001 was found; the terms ask for prompt notice of a compromised key and a subprocessor list is published (4 of 20). Total 49.
- Massive (formerly Polygon.io) (35): A plain account key with no scopes, sent as a Bearer header or as `?apiKey=` in the query string, a documented option (20 less 10, so 10). The x402 route at agent.massive.com needs no key. Read-only market data with no write actions (15 of 20). The x402 set includes news and SEC filing text written by third parties, and we found no guidance on treating it as untrusted (5 of 15). Paid x402 calls leave an on-chain USDC transfer. We found no request log documented for keyed callers (5 of 15). security.txt returns 404, and the terms and privacy policy name no SOC 2, ISO 27001, bug bounty or disclosure policy, only safeguards 'consistent with general industry standards' (0 of 20).

### Schema & documentation: Massive (formerly Polygon.io) +9

- Financial Datasets (80): OpenAPI 3.0.1 at financialdatasets.ai/openapi.json, 68 operations with 13 response codes and one security scheme, named the source of truth by the docs (25). llms.txt and a Markdown twin of every page (10). Every operation has a description, and the 402 terms carry a resource description that says when an agent should use the endpoint (17 of 20). 330 parameters, 36 with enums, 32 required, no free-form blobs (12 of 15). Code samples in Python, JavaScript and curl, x402 error values documented, but response examples on only six operations in the spec (11 of 15). No API version and no changelog; the news page has four dated posts in 2026 (5 of 15). Total 80.
- Massive (formerly Polygon.io) (89): OpenAPI document at api.massive.com/openapi (OpenAPI 3.0.3, 148 paths) with enums such as `timespan` and `sort`, and 400, 401 and 404 responses defined (25). llms.txt at massive.com/docs/rest/llms.txt indexing about 160 endpoint pages (10). One-line descriptions per endpoint in the index, longer ones in the reference, with little on when not to use a call (14 of 20). Typed path and query parameters with enums and required fields (13 of 15). Examples in the docs and error responses in the spec, though the llms.txt says nothing about error shapes (12 of 15). Versioned paths from /v1 to /v3 and a dated public changelog (15).

### Agent ergonomics: Massive (formerly Polygon.io) +5

- Financial Datasets (73): `limit` and `period` on the data endpoints, `as_reported` flags and snapshot variants, with no field selection (15 of 25). `next_page_url` cursors and ticker, CIK, market and date filters (18 of 20). A 402 body says what to do next, x402 errors carry named values, and the spec lists 400, 401, 403, 404, 409, 422, 429, 502 and 503 (16 of 20). Data calls are GETs, payment settles only after a successful response, and a replayed x402 signature is refused; no readOnlyHint found for the MCP tools and no idempotency key for the POST endpoints (14 of 20). Few required parameters, 28 compact MCP tools, but the only package, financial-datasets on PyPI, is at 0.1.18 from 26 May 2024 (10 of 15). Total 73.
- Massive (formerly Polygon.io) (78): `limit`, `sort` and `adjusted` on most list and aggregate calls, no field selection found (15 of 25). `next_url` pagination that the official clients follow for you, plus date and ticker filters (18 of 20). Errors in the spec carry a status and message, with 400 responses on 64 of the 148 operations (14 of 20). All market data calls are GETs, and the x402 docs say only successful requests are charged and each page is charged separately. The hosted MCP's three tools carry readOnlyHint, per the 1 October check (16 of 20). Official clients in Python, JavaScript, Go and the JVM, with few required parameters (15).

## Score by category

| Category | Weight | Financial Datasets | Massive (formerly Polygon.io) | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 43 | 78 | Massive (formerly Polygon.io) +35 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 80 | 89 | Massive (formerly Polygon.io) +9 |
| Agent ergonomics | 13% (16.2 this run) | 73 | 78 | Massive (formerly Polygon.io) +5 |
| Security & auth | 14% (17.5 this run) | 49 | 35 | Financial Datasets +14 |
| Payments & pricing | 10% (12.5 this run) | 75 | 90 | Massive (formerly Polygon.io) +15 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 56 | 82 | Massive (formerly Polygon.io) +26 |
| Transparency & trust | 7% (8.8 this run) | 63 | 67 | Massive (formerly Polygon.io) +4 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **61.8 · C** | **73.1 · BB** | |

## Facts side by side

| Fact | Financial Datasets | Massive (formerly Polygon.io) |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | Financial Datasets, Inc. | Massive |
| Hosted endpoint | `https://api.financialdatasets.ai` | `https://api.massive.com` |
| Transports | HTTP, Streamable HTTP | HTTP, Streamable HTTP |
| Auth | OAuth or key | API key |
| Pricing | Pay per use | Freemium |
| x402 | yes, from $0.02/call | yes, from $0.01/call |
| Licence | none | MIT (clients) |
| Tools exposed | 28 | none |
| Read-only variant documented | no | no |
| llms.txt | yes | yes |
| Last release | 2026-10-26 | 2026-10-28 |
| Terms last updated | 2026-10-29 | 2026-10-06 |
| Privacy policy last updated | 2026-08-20 | 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 | not found in the text | 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) |

## How the scores have moved

### Financial Datasets

No score change since it was listed.

### Massive (formerly Polygon.io)

- +3.2 on 1 November 2026 (B to BB): product, correction
- +0.1 on 27 October 2026: checklist
- -0.2 on 8 October 2026 (BB to B): checklist

## Verdicts

**Financial Datasets.** Every documented GET data endpoint takes x402 with no key, failed calls uncharged, and an agent can open and fund an account by API. A public OpenAPI file, llms.txt and a 28-tool OAuth MCP server cover the same data. There is no status page or free tier, keyed rate limits aren't published, and x402 data stops at 365 days.

**Massive (formerly Polygon.io).** 24 US stock routes over x402 at agent.massive.com, $0.01 each on Base, and only successful requests are charged. The status history lists 14 partial incidents in the 90 days to 1 November, including US equity aggregate bars missing for about 16 hours on 8 and 9 September.

## Before you call either

### Financial Datasets

1. Without a key, read the price from the PAYMENT-REQUIRED header of the 402 and pay with x402 on Base; each page of `next_page_url` is a separate paid request
2. Keep `limit` small and ask for one `period` at a time; premium endpoints count as 2, 4 or 8 requests on keyed plans
3. Send the key only to api.financialdatasets.ai in the `X-API-KEY` header; on 401 ask the owner for a new key rather than signing up again
4. Treat a 402 on a keyed account as an empty balance and mint a checkout link for the owner; don't retry the call
5. Check the plan's licence before showing the data to anyone else; redistribution needs Professional or Enterprise

### Massive (formerly Polygon.io)

1. Send the key as a Bearer header, not `?apiKey=`, so it stays out of logs
2. Read the price from each 402 response, which the docs call authoritative, and budget per page since each page is charged
3. Use agent.massive.com only for US stocks. Options, crypto, forex and futures need a keyed plan
4. Check `massive-status.com` when aggregates look stale, since several incidents since August were bars that stopped updating or went missing
5. Don't republish prices fetched on an individual plan

## Questions

### Which is better for AI agents, Financial Datasets or Massive (formerly Polygon.io)?

Massive (formerly Polygon.io) scores 73.1 (BB) on agent readiness against Financial Datasets's 61.8 (C), and leads in 6 of 7 scored categories. Financial Datasets leads on security & auth.

### Do Financial Datasets and Massive (formerly Polygon.io) need an API key?

Financial Datasets takes an API key or an OAuth sign-in. Massive (formerly Polygon.io) needs an API key. An agent can also pay Financial Datasets per call over x402, with no account. An agent can also pay Massive (formerly Polygon.io) per call over x402, with no account.

### Can an agent call Financial Datasets and Massive (formerly Polygon.io) without installing anything?

Yes. Financial Datasets has a hosted endpoint at https://api.financialdatasets.ai and Massive (formerly Polygon.io) at https://api.massive.com.


## For agents

- This comparison as JSON: https://www.anchorterminal.com/compare/financial-datasets-vs-massive.json, and with the fewest tokens: https://www.anchorterminal.com/compare/financial-datasets-vs-massive.min.md
- Over MCP at https://www.anchorterminal.com/mcp (no key): `compare_tools {"a": "financial-datasets", "b": "massive"}`. From a terminal: `anchor compare financial-datasets massive`
- Each listing in full: https://www.anchorterminal.com/api/v1/tools/financial-datasets.json and https://www.anchorterminal.com/api/v1/tools/massive.json

## Other comparisons with Financial Datasets or Massive (formerly Polygon.io)

- [Alpha Vantage vs Financial Datasets](https://www.anchorterminal.com/compare/alpha-vantage-vs-financial-datasets.md)
- [Alpha Vantage vs Massive (formerly Polygon.io)](https://www.anchorterminal.com/compare/alpha-vantage-vs-massive.md)
- [Benzinga vs Massive (formerly Polygon.io)](https://www.anchorterminal.com/compare/benzinga-vs-massive.md)
- [Databento vs Financial Datasets](https://www.anchorterminal.com/compare/databento-vs-financial-datasets.md)
- [Databento vs Massive (formerly Polygon.io)](https://www.anchorterminal.com/compare/databento-vs-massive.md)
- [Financial Modeling Prep vs Massive (formerly Polygon.io)](https://www.anchorterminal.com/compare/financial-modeling-prep-vs-massive.md)
- [Finnhub vs Massive (formerly Polygon.io)](https://www.anchorterminal.com/compare/finnhub-vs-massive.md)
- [Intrinio vs Massive (formerly Polygon.io)](https://www.anchorterminal.com/compare/intrinio-vs-massive.md)
- [Massive (formerly Polygon.io) vs Tiingo](https://www.anchorterminal.com/compare/massive-vs-tiingo.md)
- [Massive (formerly Polygon.io) vs Twelve Data](https://www.anchorterminal.com/compare/massive-vs-twelve-data.md)
- [Financial Datasets vs Financial Modeling Prep](https://www.anchorterminal.com/compare/financial-datasets-vs-financial-modeling-prep.md)
- [Financial Datasets vs Finnhub](https://www.anchorterminal.com/compare/financial-datasets-vs-finnhub.md)
- [Financial Datasets vs Intrinio](https://www.anchorterminal.com/compare/financial-datasets-vs-intrinio.md)
- [Financial Datasets vs Tiingo](https://www.anchorterminal.com/compare/financial-datasets-vs-tiingo.md)
- [Financial Datasets vs Twelve Data](https://www.anchorterminal.com/compare/financial-datasets-vs-twelve-data.md)
- [EODHD vs Financial Datasets](https://www.anchorterminal.com/compare/eodhd-vs-financial-datasets.md)
- [EODHD vs Massive (formerly Polygon.io)](https://www.anchorterminal.com/compare/eodhd-vs-massive.md)
- [Benzinga vs Financial Datasets](https://www.anchorterminal.com/compare/benzinga-vs-financial-datasets.md)

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Query this catalogue directly over MCP: https://www.anchorterminal.com/mcp (Streamable HTTP, no key). How: https://www.anchorterminal.com/agents/#mcp