diff --git a/internal/anime/browse_handler.go b/internal/anime/browse_handler.go
index 57a658f..af1cf86 100644
--- a/internal/anime/browse_handler.go
+++ b/internal/anime/browse_handler.go
@@ -35,17 +35,19 @@ type browseQuery struct {
 func producerQueryParams(c *gin.Context) (string, int, int, error) {
 	q := strings.TrimSpace(c.Query("q"))
 
-	page, err := strconv.Atoi(c.DefaultQuery("page", "1"))
+	rawPage := c.DefaultQuery("page", "1")
+	page, err := strconv.Atoi(rawPage)
 	if err != nil {
-		return "", 0, 0, fmt.Errorf("invalid page")
+		return "", 0, 0, fmt.Errorf("invalid page %q: %w", rawPage, err)
 	}
 	if page < 1 {
 		page = 1
 	}
 
-	limit, err := strconv.Atoi(c.DefaultQuery("limit", "50"))
+	rawLimit := c.DefaultQuery("limit", "50")
+	limit, err := strconv.Atoi(rawLimit)
 	if err != nil {
-		return "", 0, 0, fmt.Errorf("invalid limit")
+		return "", 0, 0, fmt.Errorf("invalid limit %q: %w", rawLimit, err)
 	}
 	if limit < 1 || limit > 12 {
 		limit = 12
@@ -137,8 +139,11 @@ func parseBrowseQuery(c *gin.Context) (browseQuery, error) {
 	studioID := 0
 	if raw := strings.TrimSpace(c.Query("studio")); raw != "" {
 		id, err := strconv.Atoi(raw)
-		if err != nil || id < 0 {
-			return browseQuery{}, fmt.Errorf("invalid studio id")
+		if err != nil {
+			return browseQuery{}, fmt.Errorf("invalid studio id %q: %w", raw, err)
+		}
+		if id < 0 {
+			return browseQuery{}, fmt.Errorf("invalid studio id %d", id)
 		}
 		studioID = id
 	}
@@ -147,16 +152,17 @@ func parseBrowseQuery(c *gin.Context) (browseQuery, error) {
 	for _, g := range c.QueryArray("genres") {
 		id, err := strconv.Atoi(g)
 		if err != nil {
-			return browseQuery{}, fmt.Errorf("invalid genre id")
+			return browseQuery{}, fmt.Errorf("invalid genre id %q: %w", g, err)
 		}
 		if id > 0 {
 			genres = append(genres, id)
 		}
 	}
 
-	page, err := strconv.Atoi(c.DefaultQuery("page", "1"))
+	rawPage := c.DefaultQuery("page", "1")
+	page, err := strconv.Atoi(rawPage)
 	if err != nil {
-		return browseQuery{}, fmt.Errorf("invalid page")
+		return browseQuery{}, fmt.Errorf("invalid page %q: %w", rawPage, err)
 	}
 	if page < 1 {
 		page = 1
diff --git a/internal/anime/recommendations/engine.go b/internal/anime/recommendations/engine.go
index 372726e..c1a0dd5 100644
--- a/internal/anime/recommendations/engine.go
+++ b/internal/anime/recommendations/engine.go
@@ -2,6 +2,7 @@ package recommendations
 
 import (
 	"context"
+	"fmt"
 	"mal/integrations/jikan"
 	"mal/internal/domain"
 	"mal/internal/observability"
@@ -35,7 +36,7 @@ func (e engine) getTopPicksForYou(ctx context.Context, userID string, resultLimi
 
 	watchlist, err := e.repo.GetUserWatchList(ctx, userID)
 	if err != nil {
-		return domain.CatalogSectionData{}, err
+		return domain.CatalogSectionData{}, fmt.Errorf("get user watchlist for %q: %w", userID, err)
 	}
 
 	now := time.Now()
@@ -46,17 +47,17 @@ func (e engine) getTopPicksForYou(ctx context.Context, userID string, resultLimi
 
 	seedAnimes, err := e.fetchSeedAnimes(ctx, seedPool)
 	if err != nil {
-		return domain.CatalogSectionData{}, err
+		return domain.CatalogSectionData{}, fmt.Errorf("fetch seed animes: %w", err)
 	}
 
 	profile := buildTasteProfile(now, seedPool, seedAnimes)
 	store := newCandidateStore(watchlist)
 
 	if err := e.collectCollaborativeCandidates(ctx, seedPool, store); err != nil {
-		return domain.CatalogSectionData{}, err
+		return domain.CatalogSectionData{}, fmt.Errorf("collect collaborative candidates: %w", err)
 	}
 	if err := e.collectProfileSearchCandidates(ctx, profile, store); err != nil {
-		return domain.CatalogSectionData{}, err
+		return domain.CatalogSectionData{}, fmt.Errorf("collect profile search candidates: %w", err)
 	}
 
 	ranked := store.ranked()
@@ -66,7 +67,7 @@ func (e engine) getTopPicksForYou(ctx context.Context, userID string, resultLimi
 
 	candidates, err := e.scoreRankedCandidates(ctx, now, profile, ranked, resultLimit)
 	if err != nil {
-		return domain.CatalogSectionData{}, err
+		return domain.CatalogSectionData{}, fmt.Errorf("score ranked candidates: %w", err)
 	}
 
 	return domain.CatalogSectionData{
@@ -83,7 +84,7 @@ func (e engine) fetchSeedAnimes(ctx context.Context, seedPool []recommendationSe
 		g.Go(func() error {
 			anime, err := e.jikan.GetAnimeByID(ctx, seed.animeID)
 			if err != nil {
-				return err
+				return fmt.Errorf("get seed anime %d: %w", seed.animeID, err)
 			}
 			seedAnimes[i] = anime
 			return nil
@@ -91,7 +92,7 @@ func (e engine) fetchSeedAnimes(ctx context.Context, seedPool []recommendationSe
 	}
 
 	if err := g.Wait(); err != nil {
-		return nil, err
+		return nil, fmt.Errorf("wait for seed anime fetches: %w", err)
 	}
 
 	return seedAnimes, nil
@@ -131,7 +132,10 @@ func (e engine) collectCollaborativeCandidates(ctx context.Context, seedPool []r
 		})
 	}
 
-	return g.Wait()
+	if err := g.Wait(); err != nil {
+		return fmt.Errorf("wait for collaborative candidate fetches: %w", err)
+	}
+	return nil
 }
 
 func (e engine) collectProfileSearchCandidates(ctx context.Context, profile userTasteProfile, store *candidateStore) error {
@@ -183,7 +187,10 @@ func (e engine) collectProfileSearchCandidates(ctx context.Context, profile user
 		})
 	}
 
-	return g.Wait()
+	if err := g.Wait(); err != nil {
+		return fmt.Errorf("wait for profile search candidate fetches: %w", err)
+	}
+	return nil
 }
 
 func (e engine) scoreRankedCandidates(
@@ -233,7 +240,7 @@ func (e engine) scoreRankedCandidates(
 	}
 
 	if err := g.Wait(); err != nil {
-		return nil, err
+		return nil, fmt.Errorf("wait for candidate scoring: %w", err)
 	}
 
 	sort.Slice(candidates, func(i, j int) bool {
diff --git a/internal/anime/reviews_handler.go b/internal/anime/reviews_handler.go
index 11cc375..e1debb4 100644
--- a/internal/anime/reviews_handler.go
+++ b/internal/anime/reviews_handler.go
@@ -15,14 +15,19 @@ type reviewsQuery struct {
 }
 
 func parseReviewsQuery(c *gin.Context) (reviewsQuery, error) {
-	id, err := strconv.Atoi(c.Param("id"))
-	if err != nil || id <= 0 {
-		return reviewsQuery{}, fmt.Errorf("invalid anime id")
+	rawID := c.Param("id")
+	id, err := strconv.Atoi(rawID)
+	if err != nil {
+		return reviewsQuery{}, fmt.Errorf("invalid anime id %q: %w", rawID, err)
+	}
+	if id <= 0 {
+		return reviewsQuery{}, fmt.Errorf("invalid anime id %d", id)
 	}
 
-	page, err := strconv.Atoi(c.DefaultQuery("page", "1"))
+	rawPage := c.DefaultQuery("page", "1")
+	page, err := strconv.Atoi(rawPage)
 	if err != nil {
-		return reviewsQuery{}, fmt.Errorf("invalid page")
+		return reviewsQuery{}, fmt.Errorf("invalid page %q: %w", rawPage, err)
 	}
 	if page < 1 {
 		page = 1
diff --git a/internal/anime/service.go b/internal/anime/service.go
index d193c84..96ddcf9 100644
--- a/internal/anime/service.go
+++ b/internal/anime/service.go
@@ -47,19 +47,25 @@ func (s *animeService) GetCatalogSection(ctx context.Context, userID string, sec
 		case "Popular":
 			res, err = s.jikan.GetTopAnime(gCtx, 1)
 		}
-		return err
+		if err != nil {
+			return fmt.Errorf("get catalog section %q: %w", section, err)
+		}
+		return nil
 	})
 
 	if userID != "" && section == "Continue" {
 		g.Go(func() error {
 			var err error
 			cw, err = s.repo.GetContinueWatchingEntries(gCtx, userID)
-			return err
+			if err != nil {
+				return fmt.Errorf("get continue watching entries for %q: %w", userID, err)
+			}
+			return nil
 		})
 	}
 
 	if err := g.Wait(); err != nil {
-		return domain.CatalogSectionData{}, err
+		return domain.CatalogSectionData{}, fmt.Errorf("wait for catalog section %q: %w", section, err)
 	}
 
 	animes := wrapAnimes(res.Animes)
@@ -300,7 +306,7 @@ func (s *animeService) GetRandomAnime(ctx context.Context) (domain.Anime, error)
 		return domain.Anime{Anime: res.Animes[r.Intn(len(res.Animes))]}, nil
 	}
 
-	return domain.Anime{}, err
+	return domain.Anime{}, fmt.Errorf("get random anime: %w", err)
 }
 
 func (s *animeService) GetAllEpisodes(ctx context.Context, id int) ([]domain.EpisodeData, error) {