diff --git a/crates/ledger-import/src/chart_csv.rs b/crates/ledger-import/src/chart_csv.rs
index b3bfad2..47d1d89 100644
--- a/crates/ledger-import/src/chart_csv.rs
+++ b/crates/ledger-import/src/chart_csv.rs
@@ -56,6 +56,21 @@ pub enum ChartCsvError {
 
 /// Parse a chart CSV. Returns rows in file order (parents should come first,
 /// but order is not validated here).
+///
+/// ```text
+/// GOAL: read a chart of accounts a person hands the agent.
+/// SOURCE: docs/mcp-interface.md (books.import_chart_csv); CONVENTION for
+///         the layout.
+/// INVARIANTS:
+///   1. The first non-blank row is the header, exactly code,name,type,
+///      parent_code with an optional fifth tax_category (any case);
+///      anything else is BadHeader.
+///   2. Every later row has the header's width (BadColumnCount), a type
+///      among asset, liability, equity, revenue, expense, any case
+///      (BadType), and a non-blank code and name (Blank, with its row).
+///   3. A blank parent or tax category is None; blank lines are skipped;
+///      an empty file is no rows.
+/// ```
 pub fn parse_chart_csv(text: &str) -> Result<Vec<ChartRow>, ChartCsvError> {
     let mut reader = csv::ReaderBuilder::new()
         .has_headers(false)
@@ -64,13 +79,15 @@ pub fn parse_chart_csv(text: &str) -> Result<Vec<ChartRow>, ChartCsvError> {
         .from_reader(text.as_bytes());
     let mut out = Vec::new();
     let mut width = 4;
+    let mut header_seen = false;
     for (idx, record) in reader.records().enumerate() {
         let record = record.map_err(|e| ChartCsvError::Csv(e.to_string()))?;
         let fields: Vec<&str> = record.iter().collect();
         if fields.iter().all(|f| f.is_empty()) {
             continue;
         }
-        if idx == 0 {
+        if !header_seen {
+            header_seen = true;
             let lower: Vec<String> = fields.iter().map(|f| f.to_lowercase()).collect();
             width = if lower == ["code", "name", "type", "parent_code"] {
                 4
diff --git a/crates/ledger-import/src/pdf.rs b/crates/ledger-import/src/pdf.rs
index e653617..aaaeb7f 100644
--- a/crates/ledger-import/src/pdf.rs
+++ b/crates/ledger-import/src/pdf.rs
@@ -98,6 +98,19 @@ fn typeset(st: &Statement, meta: &ReportMeta) -> Result<PagedDocument, PdfError>
 }
 
 /// Render a laid-out statement (see [`crate::report`]) as a PDF.
+///
+/// ```text
+/// GOAL: a statement a CPA can print and file.
+/// SOURCE: CONVENTION (layout); docs/spec/sources/irs-records.md (records
+///         "capable of being processed", reproducible).
+/// INVARIANTS:
+///   1. Deterministic: the same statement and metadata render to the same
+///      bytes.
+///   2. Every label is data, never markup: a name holding Typst syntax
+///      ("#panic()", "*", "$", "[") prints as text and NEVER runs.
+///   3. Every row reaches the page: template_data carries each row's label,
+///      kind, and amounts split by amount_parts, in order.
+/// ```
 pub fn statement_pdf(st: &Statement, meta: &ReportMeta) -> Result<Vec<u8>, PdfError> {
     let doc = typeset(st, meta)?;
     typst_pdf::pdf(&doc, &typst_pdf::PdfOptions::default())
diff --git a/crates/ledger-import/src/xlsx.rs b/crates/ledger-import/src/xlsx.rs
index da33a65..e55643c 100644
--- a/crates/ledger-import/src/xlsx.rs
+++ b/crates/ledger-import/src/xlsx.rs
@@ -163,6 +163,19 @@ fn number(
 }
 
 /// Render a report to XLSX bytes.
+///
+/// ```text
+/// GOAL: a statement as a spreadsheet a CPA can sum and check.
+/// SOURCE: docs/spec/sources/xlsx-numbers.md (a cell number is a binary
+///         double; Excel honors 15 significant digits).
+/// INVARIANTS:
+///   1. An amount is a number cell, in an accounting format (thousands
+///      separators, negatives in parentheses), unless Excel couldn't show
+///      it exactly (finer than a cent, or past 15 digits): then its exact
+///      text, right-aligned. NEVER a number Excel would show wrong.
+///   2. Every statement row is a row, in order, with its label.
+///   3. The output is a valid XLSX (a zip holding a workbook).
+/// ```
 pub fn report_to_xlsx(report: &XlsxReport<'_>, meta: &ReportMeta) -> Result<Vec<u8>, XlsxError> {
     let mut workbook = Workbook::new();
     let sheet = workbook.add_worksheet();