Email Generation

Email Generation (Renderer)

Render a sequence from a fixed template set (sequence.md from email-prompt-building) and a contact CSV whose {{input_fields}} are already populated. This skill is mechanical: route variants, substitute placeholders, render to the target format, write the output CSV.

There is no LLM call here. All strategic reasoning happened at design time (email-prompt-building); all per-row intelligence happened upstream in normalization + enrichment, which filled the input fields. If an email is wrong, the template or the input data is wrong — fix the source, re-render.

Architectural Principle

This skill is a renderer, not a reasoner and not a runner.

template set (sequence.md) ─┐
                            ├──▶ route variant ─▶ substitute ─▶ render to target ──▶ emails CSV
contact CSV (fields filled) ┘

Inputs Required

The contact CSV must carry every field in the template's Input Fields contract, plus the routing key(s). If a declared field is missing for a row, apply that field's declared fallback; if the row can't be salvaged, drop it and report.

The Render Contract

Rendering is where this pipeline actually breaks. "Substitute the placeholders" hand-waves the hard part — newlines and escaping. This contract is mandatory.

Newline model

The template uses two break types and the renderer MUST preserve the distinction:

• \n\n (blank line) = paragraph break
• \n (single) = soft line break inside a paragraph (used deliberately)

Render targets — one body, three outputs

Order of operations — non-negotiable

1. Route variant — pick the touch variant using the routing key (e.g. customer_segment).
2. Substitute {{fields}} into the plain-text body.
3. Escape + newline-convert LAST, on the fully-assembled string.

Why this order: if you HTML-escape the template before substitution, a field value like Johnson & Johnson slips in unescaped and breaks the HTML. Escaping the final assembled string covers both template copy and substituted values.

Reference renderer

import html

def render(body: str, target: str) -> str:
    """body: assembled plain-text (variant chosen, {{fields}} substituted).
    target: 'review' | 'html' | 'plain'."""
    if target in ("review", "plain"):
        return body
    if target == "html":
        # escape content per line, THEN join with <br /> — never escape the tags
        return "<br />".join(html.escape(line) for line in body.split("\n"))
    raise ValueError(target)

Failure modes the renderer must guard against

• #1 bug — forgetting \n → <br>: the email arrives as one wall of text. Every HTML sequencer needs the conversion.
• Escaping before substitution — field values with & < > break the HTML.
• Double-escaping — &. Escape exactly once, as the last step.
• Unquoted multiline CSV cell — embedded newlines in the body column shift rows/columns. Use a real CSV writer.
• Unsubstituted placeholders — the renderer MUST assert zero {{ remain in any output before writing. A leftover {{company_name}} means the field wasn't passed (e.g. Touch 3 not receiving company_name).

Workflow

Step 1: Validate inputs

• Read the template set; collect every {{field}} and every routing key.
• Read the contact CSV headers; confirm every declared input field + routing key is present.
• Report any mismatch and stop before rendering.

Step 2: Render per row

For each contact, for each touch:

1. Route the variant (if the touch has variants).
2. Substitute input fields into the plain-text body; apply per-field fallback when a value is empty.
3. Render to each required target (review, html).
4. Assert no {{ remains.

Subject lines: first touch only; follow-ups carry an empty subject (thread continuation).

Step 3: Write outputs

• An emails CSV — one row per (contact × touch): email, first_name, company_name, touch, variant, subject, body, body_html, gaps. The gaps column records which fields fell back (e.g. industry=fallback).
• A human-readable review file — one email per section.

Write both into the GTM project's campaign-assets location. See references/render_emails.py for the reference renderer.

Step 4: Quality checks

• Zero unsubstituted {{ across all rows
• Variant routing correct — spot-check one row per variant
• \n\n and \n both survive into the HTML target as <br /><br /> / <br />
• A field value containing & / < renders escaped (not raw, not double-escaped)
• Row count = contacts × touches; gaps populated where fallbacks fired
• Follow-up touches have empty subject

Feedback Loop

When the user flags a bad email:

1. Identify whether it's a copy problem (→ fix the template via email-prompt-building) or a data problem (→ fix normalization/enrichment so the input field is correct).
2. Re-render. Never hand-edit an individual email — the fix is always in the template or the input data.

Suppression

Before writing the output CSV, drop any contact whose email is on the GTM project's suppression list (unsubscribes, bounces, retired addresses). The project owns where that list lives; this skill only honors it.

No template yet?

If no sequence.md exists for the campaign, use the email-prompt-building skill to design one. Do not improvise copy in this skill — this skill only renders.