Engagement Score

The Engagement Score (ES) is the core metric that makes YouthChain different. It is derived entirely from on-chain data via the EngagementOracle contract.

Action types and weights

Action	Enum	Weight (ES points)
`post`	0	1.00
`like`	1	0.20
`share`	2	0.50
`comment`	3	0.30
`watch`	4	0.15
`nft_create`	5	2.00
`tip`	6	0.80

Weights are compile-time constants in EngagementOracle._actionWeight — changing one requires a contract redeploy, not a governance transaction.

Decay

The contract keeps a per-action-type EMA and applies lazy decay on read: every time an action is recorded, each EMA is reduced in proportion to the seconds elapsed since that user’s last update, then the acting type’s EMA is incremented by 1.0.

λ        = 0.015 per day          (whitepaper §9.1 — a ~46-day half-life)
ema(a)  ←  ema(a) × (1 − λ × Δt)  clamped at zero
ema(t)  ←  ema(t) + 1.0           for the action just recorded

Two consequences worth designing around:

The implementation is the linear approximation of exponential decay, not a true 0.5 ^ (Δt / half_life) curve. It tracks the paper’s macro behaviour, not its exact shape.
Because 1 / 0.015 ≈ 66.7, an EMA that goes more than ~67 days without an update decays to exactly zero in one step.

Formula

raw            = Σ_a  ACT_W[a] × EMA[a]
diversity_mult = 1 + (distinct_actions − 1) × 0.05     capped at +30%
stake_mult     = 1 + 0.10 × min(1, stake / 5000)       capped at +10%

ES = clamp(raw × diversity_mult × stake_mult, 0, 100)

distinct_actions counts the action types whose EMA is above 0.1. stake is pushed in by the slasher/oracle role (setStake), so an address with no recorded stake simply gets stake_mult = 1.

There is no wallet-age, social-graph or device/IP quality term in the ES. The only “quality” factor in the protocol lives in the reward path: YCRRewards scales a claim by 0.60 + 0.40 × (activeActionTypes / 7), so a user who only ever likes claims at 60% while one active across all seven types claims at 100%. Claims are also capped at 500 YCR per address per day (DAILY_CAP) — surface that cap in your UI, or users will read a truncated claim as a bug.

Tiers

The mobile API returns a human-readable tier alongside the raw score:

Tier	ES range
`Unranked`	ES < 1.0
`Bronze`	1.0 ≤ ES < 2.0
`Silver`	2.0 ≤ ES < 5.0
`Gold`	5.0 ≤ ES < 10.0
`Diamond`	ES ≥ 10.0

Where ES is used

Leader election

PoeEngine::select_validator_index_for weights validator probabilities by stake × (1 + β·ES) (β=0.10); on the 4-node testnet the ES term is inert.

Staking Jars payout

Each “jar” redistributes rewards proportional to the ES of its stakers.

Quadratic Voting

DAO vote weight is sqrt(ES) — prevents whales from dominating.

Precompile `0x0A`

Any Solidity contract can read ES(addr) at near-zero gas via precompile.

Reading ES

JSON-RPC
Solidity
Mobile API

curl -X POST https://rpc.chain.youthapp.io \
  -H 'Content-Type: application/json' \
  -d '{
    "jsonrpc":"2.0",
    "method":"yc_getEngagementScore",
    "params":["0x0ffb0d05edcc648bc5dd06e844490b98384df4a1"],
    "id":1
  }'

interface IEngagementOracle {
  function scoreOf(address user) external view returns (uint256);
}

uint256 es = IEngagementOracle(0x2300...9ac0).scoreOf(msg.sender);
require(es >= 5e18, "Gold tier required"); // ES is scaled 1e18

curl https://api.chain.youthapp.io/api/mobile/profile/0x0ffb...
# { ..., "engagementScore": 1.2, "tier": "Bronze", ... }

Get Started

Concepts

Resources

Action types and weights

Decay

Formula

Tiers

Where ES is used

Leader election

Staking Jars payout

Quadratic Voting

Precompile `0x0A`

Reading ES

​Action types and weights

​Decay

​Formula

​Tiers

​Where ES is used

Leader election

Staking Jars payout

Quadratic Voting

Precompile 0x0A

​Reading ES

Action types and weights

Decay

Formula

Tiers

Where ES is used

Precompile `0x0A`

Reading ES