diff --git a/internal/tools/file_write_branch.go b/internal/tools/file_write_branch.go
index 8362d49..76c038f 100644
--- a/internal/tools/file_write_branch.go
+++ b/internal/tools/file_write_branch.go
@@ -23,7 +23,7 @@ func NewFileWriteBranch(c *gitea.Client, a *allowlist.Allowlist) *FileWriteBranc
 func (t *FileWriteBranch) Descriptor() registry.ToolDescriptor {
 	return registry.ToolDescriptor{
 		Name:        "file_write_branch",
-		Description: "Create or update a file on a feature branch. Branch is created from base if it doesn't exist.",
+		Description: "Create or update a file on the given branch. Pass an existing branch — e.g. the default branch `main` — to commit directly to it (trunk-based); a branch that doesn't exist yet is created from `base` first (PR flow). Pair with pr_create/pr_merge for the branch→PR→merge path.",
 		InputSchema: json.RawMessage(`{
 			"type":"object",
 			"properties":{