> ## Documentation Index
> Fetch the complete documentation index at: https://www.worldmonitor.app/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# News Credibility Score

> How WorldMonitor scores per-headline source reliability separately from newsworthiness — source tier, propaganda risk, independent corroboration, and the state-media cap.

This page is the canonical public methodology for the per-headline
`credibilityScore` field on `NewsItem`
(`GET /api/news/v1/list-feed-digest`, proto
`worldmonitor.news.v1.NewsItem.credibility_score`).

`credibilityScore` and `importanceScore` answer different questions. Mixing
them is the flaw a sophisticated buyer finds first.

| Score              | Question                                           | Typical high scorer                                 |
| ------------------ | -------------------------------------------------- | --------------------------------------------------- |
| `importanceScore`  | How newsworthy is this right now?                  | A critical RT flash on a diplomacy/flashpoint event |
| `credibilityScore` | How much should I trust this source on this story? | The same story reported by Reuters                  |

A state-controlled outlet can score **high** on importance and **low** on
credibility at the same time. That split is the product.

The pipeline is automated. There is no human review queue. Quality comes from
the curated source-tier table, the fail-closed propaganda-risk registry, and
digest corroboration counts that already exist. Third-party bias/factuality
ratings (AllSides, MBFC) are reserved and **not currently applied**.

## Inputs

Only inputs that bear on truthfulness enter the score. Severity, recency, and
the diplomacy/flashpoint boost stay on `importanceScore`.

| Component                 | Weight | Source                                                 |
| ------------------------- | ------ | ------------------------------------------------------ |
| Propaganda risk           | `0.50` | `shared/source-provenance.ts` `SOURCE_PROPAGANDA_RISK` |
| Source tier               | `0.30` | `shared/source-tiers.json`                             |
| Independent corroboration | `0.20` | Digest story-identity / entity corroboration count     |

Weights sum to `1.0`. The implementation is `shared/news-credibility.js`
(`computeCredibilityScore`). The digest writes the field after classification
and corroboration, alongside — not instead of — `importanceScore`.

## Component Maps

Source tier maps to:

| Tier          | Score | Meaning                            |
| ------------- | ----- | ---------------------------------- |
| `1`           | `100` | Wire / official                    |
| `2`           | `75`  | Major established outlet           |
| `3`           | `50`  | Specialty / regional               |
| `4` (default) | `25`  | Aggregator, blog, or unlisted feed |

Propaganda risk maps to:

| Risk      | Score | Meaning                                                      |
| --------- | ----- | ------------------------------------------------------------ |
| `low`     | `100` | Reviewed independent journalism                              |
| `medium`  | `50`  | State-affiliated or known editorial tilt                     |
| `unknown` | `35`  | Not yet reviewed — fail-closed, never treated as independent |
| `high`    | `12`  | State-controlled media                                       |

Unlisted sources default to `unknown`, not `low`. That fail-closed default is
the same contract as the provenance badges.

Independent corroboration uses the digest's existing corroboration count (the
larger of story-identity cluster size and entity-level corroboration), capped
at five sources, with `20` points per source before the `0.20` weight. This
is the same corroboration signal `importanceScore` already consumes; it is
not a second clustering pass.

## High-Risk Cap

After the weighted sum is rounded and clamped to `0–100`, a source whose
propaganda risk is `high` is capped at `40`.

The cap is the acceptance gate for state media. An RT or TASS item can still
pick up corroboration points when independent outlets also report the event,
but it cannot look like a high-credibility wire. Reuters with no extra
corroboration scores around `80`; RT with none scores in the low `20`s.

## What This Score Is Not

* It is **not** a statement that the underlying event is false. A true event
  reported first by state media still has low *source* credibility until
  independent outlets corroborate it.
* It is **not** AllSides or MBFC. Those ratings are out of scope until a
  dedicated ingest exists.
* It is **not** used to sort the news list. Relevance sort remains
  `importanceScore`, then publication time. Credibility is displayed, not
  substituted for newsworthiness.
* Same-ecosystem inflation remains a known limitation: five Russian state
  desks clustering on one headline still share one high-risk cap, but the
  corroboration count is the digest's existing publisher-family signal, not a
  new independence classifier.

## Surfaces

| Surface                                | Field                                                |
| -------------------------------------- | ---------------------------------------------------- |
| Feed digest API                        | `NewsItem.credibilityScore`                          |
| News list UI                           | `CRED NN` badge on flat items and clustered cards    |
| Insights / MCP `get_news_intelligence` | `topStories[].credibilityScore`                      |
| MCP `get_news_clusters`                | `clusters[].credibilityScore` for the primary outlet |

## Source Files

* Scorer: `shared/news-credibility.js`
* Digest writer: `server/worldmonitor/news/v1/list-feed-digest.ts`
* API contract: `proto/worldmonitor/news/v1/news_item.proto`
* Provenance registry: `shared/source-provenance.ts`
* Tier table: `shared/source-tiers.json`
* News list render: `src/components/news/source-provenance.ts`,
  `src/components/NewsPanel.ts`
* Pipeline sibling: [News Digest and Briefing](/docs/methodology/news-digest-and-briefing)