diff --git a/README.md b/README.md
index ea43113..0220f92 100644
--- a/README.md
+++ b/README.md
@@ -48,7 +48,9 @@ In priority order.
 6. **Failures are values.** Nothing throws, and `code` is a closed list — as much a contract as
    the emitted formats are.
 7. **Nothing in the way.** No runtime dependencies, no I/O, no configuration, no host API: ESM on
-   any ES2022 engine, in a browser as readily as on a server, installed from public npm.
+   any ES2022 engine, in a browser as readily as on a server, installed from public npm. The public
+   surface is the conversions, their types, `isAdfDocument`, and what a consumer needs to check a
+   guarantee this README makes; a helper is exported only when a persona cannot do without it.
 8. **Correct before fast.** Each format means what its own specification says — markdown as the
    CommonMark spec reads it, well-formed HTML as the HTML standard parses it — both in what this
    library reads and in what a conforming parser reads from what it writes. A call takes a whole
diff --git a/todo.md b/todo.md
index 4fe3242..f119bfc 100644
--- a/todo.md
+++ b/todo.md
@@ -2,6 +2,10 @@
 
 ## 0.2.0
 
+- **39 — Export `sameAdf(a, b)`, the equality README §The guarantees means.** Per Goal 7, it answers
+  whether two documents are equal editor-normal (`docs/decisions.md` §Equality is editor-normal), and
+  the guarantees' "equals `doc`" names it, since a deep-equal fails on a valid document holding an
+  empty `attrs` or two adjacent text nodes with the same marks.
 - **35 — Read and write plain markdown as a flavour of the markdown grammar.** Per Goal 2 and
   `docs/decisions.md` §Plain markdown is a flavour of the grammar, README §Plain markdown's rows are
   read by `markdownToAdf`'s parser and written by `adfToMarkdown`'s writer, and the lift goes. The