Documentation

Everything you need to build with DeepInquiry — the API, the verification pipeline, the embeddable widget, and the CiteSig signature protocol.

Getting started

Get an API key →
Sign up for a free key (500 requests/month). No card required.
API overview →
Endpoints, authentication, and pricing.
Response fields →
What each fact response contains, with a sample.
MCP server →
Use DeepInquiry facts from AI agents.
Plans and quotas →
Free, Starter, Growth, Scale, Enterprise.

Verification

Verification methodology →
How we grade facts on how distinct their sources are — the pipeline that groups sources by website and mapped parent company, sets aside mirrors, and computes a 0–1 score.
Two sources are not always two sources →
Why we group sources by website and parent company before counting them.
How to cite a verified fact in your AI app →
Showing a fact, its sources and its tier in an application.
Fact tiers
Gold, Silver, Bronze: graded on how many separate source groups support the fact and how much they differ (see plans for the exact thresholds). Unverified: below Bronze; returned only to opt-in audit-mode consumers.

API reference

GET /api/v1/facts/random
Returns one random verified fact with citations.
GET /api/v1/facts?category=X&era=Y&limit=N
Filtered list. Supports pagination via cursor.
GET /api/v1/facts/:id
Single fact lookup with full source graph and CiteSig signature.
GET /api/v1/topics
List of available topic categories.

Authentication: x-api-key: YOUR_API_KEY header. Rate limits returned in X-RateLimit-* response headers.

Want to try it without writing code? Open the Postman collection, add your key, and send a request. The full machine-readable reference is at /openapi.json.

Embed widget

Free embeddable widget →
Drop a rotating verified-fact widget into any site. One line of HTML. Free for non-commercial use.

CiteSig protocol

Every DeepInquiry fact carries a CiteSig signature — an open, tamper-evident proof of provenance you can verify offline.

citesig.org — protocol homepage →
Spec, verifier extension, and reference implementations.