ADR-042: Provider Trust Score

Status: Accepted Date: 2026-02-27 Related: ADR-041 (Two-Layer Model), ADR-037 (Personal Trust Score)

Context

Layer 2 providers (ADR-041) need a trust signal that is:

Visible to anyone considering hiring the provider
Based on direct service experience, not community relationships
Separate from ADR-037 personal trust (which measures gift-economy reciprocity)

Star ratings are the established pattern for service providers. Completion record and responsiveness add behavioral signals beyond subjective ratings.

Decision

Provider trust score uses a three-component weighted formula:

provider_trust_score =
  (avg_stars_normalized * 0.60) +
  (completion_rate       * 0.30) +
  (response_rate         * 0.10)

Where:

avg_stars_normalized = ((avg_stars - 1) / 4) * 100 — maps 1–5 stars to 0–100
completion_rate = completed matches / total matches accepted (0–100)
response_rate = responded within 24h / total inquiries (0–100)

Score is an integer 0–100, cached in reputation.provider_trust_scores.

Weight Rationale

Component	Weight	Rationale
avg_stars	60%	Primary quality signal — direct experience feedback
completion_rate	30%	Reliability — did they show up and complete the job?
response_rate	10%	Responsiveness — secondary UX signal

Completion rate is weighted heavily (30%) because a provider who accepts matches and doesn't complete them is more harmful to trust than one with mediocre ratings.

Separation from ADR-037

	Personal Trust (ADR-037)	Provider Trust (ADR-042)
Measures	Reciprocity in gift economy	Service quality + reliability
Source	Feedback after mutual aid	Stars after paid service
Scope	Community-scoped	Provider-scoped (public)
Range	0–100	0–100
Decay	Yes (ADR-011)	No

Score Update Triggers

Score is recalculated immediately when a new review is submitted (via recalculateProviderTrustScore()). Completion rate and response rate are updated by match completion events (future work for Phase 2).

Review Constraints

One review per match per reviewer (enforced by UNIQUE constraint on match_id, reviewer_id)
Reviews are tied to match_id where possible to verify the reviewer actually used the service
match_id is nullable for cases where coordination happened outside Karmyq's match system

Consequences

Positive

Simple, interpretable formula
Visible score gives consumers a signal without requiring them to read all reviews
Separate from karma/personal trust — no cross-contamination

Negative / Risks

Completion rate starts at 0 for new providers — cold start problem
Phase 1 response_rate not yet tracked (defaults to 0); Phase 2 will wire match response events
Provider could game stars by self-reviewing through alt accounts (mitigated by match_id verification in Phase 2)