diff --git a/internal/skills/brain/handlers.go b/internal/skills/brain/handlers.go
index ae53e42..a79ead9 100644
--- a/internal/skills/brain/handlers.go
+++ b/internal/skills/brain/handlers.go
@@ -78,6 +78,9 @@ func (s *Skill) ingest(ctx context.Context, args json.RawMessage) (json.RawMessa
 	if s.cfg.IngestSvcURL == "" {
 		return nil, fmt.Errorf("brain_ingest: INGEST_SVC_URL not configured")
 	}
+	if a.Path != "" && a.Content != "" {
+		return nil, fmt.Errorf("path and content+source are mutually exclusive: provide one or the other")
+	}
 	if a.Path != "" {
 		return s.postTo(ctx, s.cfg.IngestSvcURL+"/ingest-path", map[string]any{
 			"path":    a.Path,
diff --git a/internal/skills/brain/skill.go b/internal/skills/brain/skill.go
index 6b6da1f..260dc5a 100644
--- a/internal/skills/brain/skill.go
+++ b/internal/skills/brain/skill.go
@@ -56,12 +56,16 @@ func (s *Skill) Tools() []registry.ToolDef {
 	}
 	if s.cfg.IngestSvcURL != "" {
 		tools = append(tools, registry.ToolDef{
-			Name:        "brain_ingest",
-			Description: "Ingest text content into the brain wiki (brain/wiki/). Calls an LLM to produce structured wiki pages. Use for substantial documents, articles, or knowledge worth structuring. Returns the list of wiki pages written.",
+			Name: "brain_ingest",
+			Description: "Ingest content into the brain wiki (brain/wiki/). Calls an LLM to produce structured wiki pages. " +
+				"Use for substantial documents, articles, or knowledge worth structuring. " +
+				"Provide EITHER (a) path — absolute path to a file or directory, " +
+				"OR (b) content + source — raw text and a human-readable name. " +
+				"Providing both is an error. Returns the list of wiki pages written.",
 			InputSchema: schema([]string{}, map[string]any{
-				"content": str,
-				"source":  map[string]any{"type": "string", "description": "human-readable name for the content, e.g. 'article-on-raft.md'"},
-				"path":    map[string]any{"type": "string", "description": "absolute path to a file or directory to ingest; if set, content and source are not needed"},
+				"content": map[string]any{"type": "string", "description": "raw text to ingest; required when path is not set"},
+				"source":  map[string]any{"type": "string", "description": "human-readable name for the content, e.g. 'shape-up-book'; required when path is not set"},
+				"path":    map[string]any{"type": "string", "description": "absolute path to a file or directory to ingest; mutually exclusive with content+source"},
 				"dry_run": map[string]any{"type": "boolean"},
 			}),
 		})