split overlong sentences

src/building/bootstrapping/writing-tools-in-bootstrap.md

@@ -3,17 +3,26 @@
 There are three types of tools you can write in bootstrap:
 
 - **`Mode::ToolBootstrap`**
+
   Use this for tools that don’t need anything from the in-tree compiler and can run with the stage0 `rustc`.
-  The output is placed in the "bootstrap-tools" directory. This mode is for general-purpose tools built
-  entirely with the stage0 compiler, including target libraries and only works for stage 0.
+  The output is placed in the "bootstrap-tools" directory.
+  This mode is for general-purpose tools built entirely with the stage0 compiler,
+  including target libraries, and it only works for stage 0.
 
 - **`Mode::ToolStd`**
-  Use this for tools that rely on the locally built std. The output goes into the "stageN-tools" directory.
+
+  Use this for tools that rely on the locally built std.
+  The output goes into the "stageN-tools" directory.
   This mode is rarely used, mainly for `compiletest` which requires `libtest`.
 
 - **`Mode::ToolRustcPrivate`**
-  Use this for tools that use the `rustc_private` mechanism, and thus depend on the locally built `rustc` and its rlib artifacts. This is more complex than the other modes because the tool must be built with the same compiler used for `rustc` and placed in the "stageN-tools" directory. When you choose `Mode::ToolRustcPrivate`, `ToolBuild` implementation takes care of this automatically. If you need to use the builder’s compiler for something specific, you can get it from `ToolBuildResult`, which is
-  returned by the tool's [`Step`].
+
+  Use this for tools that use the `rustc_private` mechanism,
+  and thus depend on the locally built `rustc` and its rlib artifacts.
+  This is more complex than the other modes because the tool must be built with the same compiler used for `rustc` and placed in the "stageN-tools" directory.
+  When you choose `Mode::ToolRustcPrivate`, `ToolBuild` implementation takes care of this automatically.
+  If you need to use the builder’s compiler for something specific,
+  you can get it from `ToolBuildResult`, which is returned by the tool's [`Step`].
 
 Regardless of the tool type you must return `ToolBuildResult` from the tool’s [`Step`] implementation and use `ToolBuild` inside it.