GET /v1/facts

Weighted facts that pass today (free, no key needed)

Weighted facts about what wins, each with its sample and its odds: e.g. 'in weight loss, EU, same brand and same launch day, video reached more people than image in 28 of 40 brands (70%, 95% interval 55-82%, p = 0.017)'. Use it when the user asks what is proven, what works better, video or image, or wants evidence rather than examples. Only facts that pass today are returned (30+ brands, p < 0.05, interval excluding 50%), with n, share, interval, p, method, read dates, caveats (always repeat them with the fact) and the commit of the code that computed them. Free.

Public: works without a key (cached 5 minutes); with a key it is logged like any call and still free. MCP tool: get_facts.

Cost: Free.

Parameters

Parameter	Type	What it does
`niche`	string	e.g. weight loss
`region`	string: `EU`, `US`

Errors

`400`	Unknown parameter or region.
`503`	No facts computed yet.

Request

curl -s "https://api.askposeidon.app/v1/facts"

Response

{
  "facts": [],
  "computed_at": "2026-11-13T06:46:02+00:00",
  "rule": "A fact is served only while status = passes: 30+ brands (one shop = one brand, purity rule applied), p < 0.05, interval excludes 50%; a fact across niches must also keep p < 0.05 when any single checked niche or main country is left out.",
  "note": "No fact passes today on hand-checked niches, so none is shown. Poseidon never shows a fact that doesn't hold.",
  "how_to_read": "Each fact counts brands, not ads: within one brand, two ads launched the same day compared on Meta's EU reach. share_a_higher is the share of brands where the first one reached more people; wilson_95 its 95% interval; sign_test_p the chance of a split this lopsided if it were 50/50. A fact is served only while it passes; it disappears if it stops passing."
}