diff --git a/internal/model/alert.go b/internal/model/alert.go
index 54fcdfc..141d933 100644
--- a/internal/model/alert.go
+++ b/internal/model/alert.go
@@ -1,23 +1,24 @@
+// FILE: internal/model/alert.go
 package model
 
 import "time"
 
 // Placeholder for NWS alerts (GeoJSON feature properties are rich).
 type WeatherAlert struct {
-	ID string
+	ID string `json:"id"`
 
-	Event       string
-	Headline    string
-	Description string
-	Instruction string
+	Event       string `json:"event,omitempty"`
+	Headline    string `json:"headline,omitempty"`
+	Description string `json:"description,omitempty"`
+	Instruction string `json:"instruction,omitempty"`
 
-	Severity  string
-	Urgency   string
-	Certainty string
+	Severity  string `json:"severity,omitempty"`
+	Urgency   string `json:"urgency,omitempty"`
+	Certainty string `json:"certainty,omitempty"`
 
-	Sent      *time.Time
-	Effective *time.Time
-	Expires   *time.Time
+	Sent      *time.Time `json:"sent,omitempty"`
+	Effective *time.Time `json:"effective,omitempty"`
+	Expires   *time.Time `json:"expires,omitempty"`
 
-	Areas []string
+	Areas []string `json:"areas,omitempty"`
 }
diff --git a/internal/model/doc.go b/internal/model/doc.go
new file mode 100644
index 0000000..1b8145e
--- /dev/null
+++ b/internal/model/doc.go
@@ -0,0 +1,10 @@
+// FILE: internal/model/doc.go
+// Package model defines weatherfeeder's canonical domain payload types.
+//
+// These structs are emitted as the Payload of canonical events (schemas "weather.*.vN").
+// JSON tags are treated as part of the wire contract for sinks (stdout today; others later).
+//
+// Compatibility guidance:
+//   - Prefer additive changes.
+//   - Avoid renaming/removing fields without a schema version bump.
+package model
diff --git a/internal/model/forecast.go b/internal/model/forecast.go
index ce2f251..45089af 100644
--- a/internal/model/forecast.go
+++ b/internal/model/forecast.go
@@ -1,17 +1,15 @@
+// FILE: internal/model/forecast.go
 package model
 
 import "time"
 
 // WeatherForecast identity fields (as you described).
 type WeatherForecast struct {
-	IssuedBy      string    // e.g. "NWS"
-	IssuedAt      time.Time // when forecast product was issued
-	ForecastType  string    // e.g. "hourly", "daily"
-	ForecastStart time.Time // start of the applicable forecast period
+	IssuedBy      string    `json:"issuedBy,omitempty"`     // e.g. "NWS"
+	IssuedAt      time.Time `json:"issuedAt"`               // when forecast product was issued
+	ForecastType  string    `json:"forecastType,omitempty"` // e.g. "hourly", "daily"
+	ForecastStart time.Time `json:"forecastStart"`          // start of the applicable forecast period
 
 	// TODO: You’ll likely want ForecastEnd too.
-
 	// TODO: Add meteorological fields you care about.
-	// Temperature, precip probability, wind, etc.
-	// Decide if you want a single "period" model or an array of periods.
 }
diff --git a/internal/model/observation.go b/internal/model/observation.go
index 071f536..5a0b621 100644
--- a/internal/model/observation.go
+++ b/internal/model/observation.go
@@ -1,72 +1,56 @@
+// FILE: internal/model/observation.go
 package model
 
 import "time"
 
 type WeatherObservation struct {
 	// Identity / metadata
-	StationID   string
-	StationName string
-	Timestamp   time.Time
+	StationID   string    `json:"stationId,omitempty"`
+	StationName string    `json:"stationName,omitempty"`
+	Timestamp   time.Time `json:"timestamp"`
 
 	// Canonical internal representation (provider-independent).
-	//
-	// ConditionCode should be populated by all sources. ConditionText should be the
-	// canonical human-readable string derived from the WMO code (not the provider's
-	// original wording).
-	//
-	// IsDay is optional; some providers supply a day/night flag (e.g., Open-Meteo),
-	// while others may not (e.g., NWS observations). When unknown, it can be nil.
-	ConditionCode WMOCode
-	ConditionText string
-	IsDay         *bool
+	ConditionCode WMOCode `json:"conditionCode"`
+	ConditionText string  `json:"conditionText,omitempty"`
+	IsDay         *bool   `json:"isDay,omitempty"`
 
 	// Provider-specific “evidence” for troubleshooting mapping and drift.
-	//
-	// This is intentionally limited: it is not intended to be used downstream for
-	// business logic. Downstream logic should rely on ConditionCode / ConditionText.
-	ProviderRawDescription string
+	ProviderRawDescription string `json:"providerRawDescription,omitempty"`
 
 	// Human-facing (legacy / transitional)
-	//
-	// TextDescription currently carries provider text in existing drivers.
-	// As we transition to WMO-based normalization, downstream presentation should
-	// switch to using ConditionText. After migration, this may be removed or repurposed.
-	TextDescription string
+	TextDescription string `json:"textDescription,omitempty"`
 
 	// Provider-specific (legacy / transitional)
-	//
-	// IconURL is not part of the canonical internal vocabulary. It's retained only
-	// because current sources populate it; it is not required for downstream systems.
-	IconURL string
+	IconURL string `json:"iconUrl,omitempty"`
 
 	// Core measurements (nullable)
-	TemperatureC *float64
-	DewpointC    *float64
+	TemperatureC *float64 `json:"temperatureC,omitempty"`
+	DewpointC    *float64 `json:"dewpointC,omitempty"`
 
-	WindDirectionDegrees *float64
-	WindSpeedKmh         *float64
-	WindGustKmh          *float64
+	WindDirectionDegrees *float64 `json:"windDirectionDegrees,omitempty"`
+	WindSpeedKmh         *float64 `json:"windSpeedKmh,omitempty"`
+	WindGustKmh          *float64 `json:"windGustKmh,omitempty"`
 
-	BarometricPressurePa *float64
-	SeaLevelPressurePa   *float64
-	VisibilityMeters     *float64
+	BarometricPressurePa *float64 `json:"barometricPressurePa,omitempty"`
+	SeaLevelPressurePa   *float64 `json:"seaLevelPressurePa,omitempty"`
+	VisibilityMeters     *float64 `json:"visibilityMeters,omitempty"`
 
-	RelativeHumidityPercent *float64
-	WindChillC              *float64
-	HeatIndexC              *float64
+	RelativeHumidityPercent *float64 `json:"relativeHumidityPercent,omitempty"`
+	WindChillC              *float64 `json:"windChillC,omitempty"`
+	HeatIndexC              *float64 `json:"heatIndexC,omitempty"`
 
-	ElevationMeters *float64
-	RawMessage      string
+	ElevationMeters *float64 `json:"elevationMeters,omitempty"`
+	RawMessage      string   `json:"rawMessage,omitempty"`
 
-	PresentWeather []PresentWeather
-	CloudLayers    []CloudLayer
+	PresentWeather []PresentWeather `json:"presentWeather,omitempty"`
+	CloudLayers    []CloudLayer     `json:"cloudLayers,omitempty"`
 }
 
 type CloudLayer struct {
-	BaseMeters *float64
-	Amount     string
+	BaseMeters *float64 `json:"baseMeters,omitempty"`
+	Amount     string   `json:"amount,omitempty"`
 }
 
 type PresentWeather struct {
-	Raw map[string]any
+	Raw map[string]any `json:"raw,omitempty"`
 }