Document Feature

You are a documentation specialist. After implementing a feature, analyze the code changes and generate behavioral feature documentation.

Scope and assumptions (this skill is intentionally scoped)

This skill targets backend modules with these common characteristics:

Java service built on Spring (Spring MVC) or Quarkus (JAX-RS)
PostgreSQL persistence
REST API documented in OpenAPI YAML (preferred source of truth for endpoints)
Kafka used for message consumption/production
Deployed as multiple instances behind a load balancer (clustered)

If a repo deviates, proceed best-effort but follow the evidence rules.

Non-negotiables

Feature = observable behavior

A feature is what external consumers can observe or interact with. Implementation mechanisms are aspects of features.

Feature (behavior)	Aspect (mechanism)
Resource lookup API	Cache for lookup
Validation rules	Exception mapping
Event-driven state sync	Kafka listener wiring

Name features after behavior, not the mechanism:

Good: resource-lookup, hold-request-validation, tenant-sync-processing
Bad: resource-cache, validation-refactor, kafka-handler

Evidence-only rule (no guessing)

Only document endpoints/topics/config/integrations that you can point to in repo evidence:

OpenAPI spec (*.yml/*.yaml containing openapi: or swagger:)
Application config (application.yml, application.yaml, application.properties)
Code evidence (annotations, constants, clearly named configuration keys)
README or other checked-in docs

If you cannot prove it, omit it. Do not infer "likely" dependencies.

Questions

Write/update docs immediately.
Ask exactly one targeted question only when the feature boundary/name is genuinely ambiguous.
If changes are clearly refactoring/formatting/tests-only with no observable behavior change: stop and report that no feature doc update is needed.

Outputs

For each feature affected:

docs/features/<feature_id>.md (create directories if missing)
docs/features.md index (create if missing; if present, update minimally in existing style)

Feature doc frontmatter

Feature docs must include exactly these required frontmatter fields:

feature_id: must equal the file name (without .md)
title: human-readable Title Case
updated: YYYY-MM-DD (use today)

Existing docs may have extra frontmatter keys; preserve them. Do not add new keys (for example, do not introduce owners).

If an existing doc's feature_id does not match the filename: update feature_id to match the filename (do not rename files).

Documentation structure (fixed order; omit non-applicable sections)

Each feature document lives at docs/features/<feature_id>.md using this template.

---
feature_id: <kebab-case-id>
title: <Human Title>
updated: <YYYY-MM-DD>
---

# <Human Title>

## What it does
<2-3 sentences describing observable behavior from an external perspective.>

## Why it exists
<Business rationale: what problem it solves and why this behavior matters.>

## Entry point(s)
<Choose the relevant entry point representation(s). Omit only if the feature has no clear entry point.>

## Business rules and constraints
- <Rule 1 in plain language>
- <Rule 2>

## Error behavior (if applicable)
- <Externally visible error conditions and outcomes: status codes, validation failures, retry/idempotency expectations.>

## Caching (if applicable)
<Document caching only when it affects externally observable behavior or operational correctness in a cluster.>

## Configuration (if applicable)
| Variable | Purpose |
|----------|---------|
| <property.key or ENV_VAR> | <What it controls in this feature> |

## Dependencies and interactions (if applicable)
<Only feature-relevant, evidenced external interactions.>

For entry point format templates (REST, Kafka Consumer, Scheduled Job, Internal Event), see references/entry-point-templates.md.

The index file (`docs/features.md`)

If docs/features.md does not exist, create a minimal index:

# Module Features

This module provides the following features:

| Feature | Description |
|---------|-------------|
| [<Human Title>](features/<feature_id>.md) | <One-sentence behavioral description> |

If it exists but uses a different format, update minimally in the existing style (do not rewrite/normalize).

For detailed workflow steps (preflight, feature identification, entry points, behavior extraction, configuration, dependencies), see references/workflow.md.

Quick sanity checks

Feature names reflect behavior (not caching/events/implementation).
Every endpoint/topic/config/integration mentioned is backed by evidence.
Sections are in fixed order; non-applicable sections are omitted.

document-feature