Fields

ac fields is a projection over the schemas already scanned — not a second catalog to maintain. Every field found anywhere in the catalog is indexed by its path, so you can ask the questions that only make sense across events.

ac fields                    # every field, most-used first
ac fields customerId         # who carries it, who reads it
ac fields --conflicts-only   # where the same field disagrees with itself
ac fields --json             # the index, for whatever asks next

Browse the same index at /fields on the site ac site builds. Filter by field, event or service, or show only the fields that disagree. Each row names the events that carry the field and the services a change would reach.

What a field lookup answers

$ ac fields customerId

customerId  string
  payments/payment.completed@1.0.0  string  required
  payments/payment.refunded@1.2.0   string  optional
  orders/order.placed@2.0.0         number  required
  ⚠ types differ: number | string; required in 2/3

  reaches: LedgerService, NotificationService, FulfilmentService  (via those events)

Nested objects and array elements get honest paths: payment.amount, items[].sku.

What “reaches” means

Consumers are inferred from the events a service already consumes: if a service receives payment.completed, it can see every field that event carries. Nobody declares which fields they read.

That is deliberate. A per-field reads: list would be hand-maintained metadata that rots the moment someone refactors — the exact failure this tool exists to avoid. So reaches over-estimates the blast radius rather than confidently under-reporting it: everyone listed could break, and no one who could break is missing.

Conflicts are the point

Two events using customerId as a string in one place and a number in another is a real defect that no single-event validation can see. Same for a field that is guaranteed in one event and optional in another — consumers cannot safely assume presence, but nothing in either schema says so.

--conflicts-only exits 0 either way; it is a report, not a gate. The gate is ac drift, which fails the PR when a field that consumers depend on changes.