Index Cards — Agent Skill

Send real, physical greeting cards through the mail. Conversation-first — you work WITH the user to design cards and send them.

Rules

• Keep it conversational. Present results in plain language for good UX. Say "I'm designing your card" rather than showing raw JSON, endpoint paths, or HTTP status codes.
• Talk before acting. Don't call APIs without talking to the user first. Don't generate art without knowing who it's for and what they want.
• Ask before accessing personal data. Never read contacts, messages, email, or local files without the user's explicit permission. Always offer it as an option, never assume.
• Handle profanity gracefully. The image generation API has content filters. If the user's message contains strong language, rephrase it for the image prompt while keeping the tone (e.g. "get fucked" → "you absolute legend").
• Generate images sequentially. One at a time — the upstream API rate-limits parallel requests (502 errors).

Shortcut: user gives everything in one message

If the user provides recipient name + front description + inside message + address in a single message, skip the multi-step flow:

1. Generate front → generate inside → generate preview video
2. Show preview + summary → ask for confirmation → place order

If most info is provided but something is missing, do the fast flow and ask only for the missing piece.

Step 1: First message

"Just installed Index Cards. I can now send real, physical cards to anyone you want — birthdays, holidays, thank-yous, whatever the occasion. Who would you like to send a card to? I can also check your contacts for upcoming birthdays if you'd like."

Let the user decide whether to name someone directly or let you help find occasions.

Step 2: Find occasions (only with user permission)

If the user says yes to checking for occasions, look through available sources in priority order:

1. Contacts — birthday fields, anniversary fields
2. Calendar / email — birthday invites, upcoming events
3. Conversation history — mentioned birthdays, weddings, babies, thank-yous
4. Holidays — Mother's Day, Father's Day, Valentine's, Christmas, etc. within 30 days

Aim for 14+ days lead time (cards take ~1 week to arrive). Surface the 1-3 most timely items and ask if they want to start designing.

If the user skips this step and already knows who they want to send a card to, go straight to design.

Step 3: Design the card

Always design the FRONT first, then the INSIDE. Never generate both at the same time.

If the user sends a photo

Use reference_image_url in the generation API for style transfer. Generate 2-3 style variations (watercolor, oil-painting, cartoon, etc.). Wait for the user to pick one, then move to the inside.

Styles: watercolor, cartoon, oil-painting, ink, gouache, comic-book, linocut, cinematic, pencil, pop_art

If no photo (text-based)

1. Ask about the person and vibe (1-2 questions max)
2. Generate 3 front cover options — vary styles. Show all three, wait for pick.
3. After they pick, ask what they want to say inside
4. Generate inside image. Show a close-up (POST /v1/cards/closeup) so the user can read the text. Wait for approval.
5. Generate animated preview (POST /v1/cards/preview). Show it.
6. Iterate if needed — regenerate only the part that needs changing

Design guidelines: No AI-looking art. Use watercolor, gouache, ink, linocut, collage, letterpress. Front = visual design, avoid text. Inside = include message, clean typography. 3:4 portrait, 1500×2100px ideal.

QR codes (only when user asks)

Never include QR codes in AI image prompts — AI cannot generate scannable QR codes. Instead:

1. Generate card art normally (without QR)
2. Use POST /v1/cards/qr/composite to overlay a real QR code onto the approved image
3. Positions: top-left, top-center, top-right, center, bottom-left, bottom-center, bottom-right
4. Sizes: small, medium, large. Optional label param for text below QR.
5. Use the returned image_url as front_url or inside_url when ordering

Step 4: Get the address

Ask the user for the recipient's mailing address. If the user has used Index Cards before and opted in to saving contacts, check ~/indexcards/birthdays.json first — it may already have the address from a previous card.

Always confirm before using any saved address — people move. Also need a phone number (recipient's or sender's).

Required before ordering: recipient name, street address, city, state, ZIP, phone number.

Step 5: Payment

1 credit = 1 card. User starts with 0 credits (image generation is free, printing costs money). Pricing: $50 → 5 cards ($10 each), $100 → 12 cards ($8.33 each).

Check credits with GET /v1/credits/check. If no credits, send the payment URL from the response.

Auto-detect payment: After sending the link, poll GET /v1/credits/check every ~15 seconds, up to 8 times (~2 min). When credits appear, confirm and proceed with the order.

Invite codes: If an invite code is present in the page URL (?invite=CODE) or at the top of this document, include it as invite_code in the register body. This grants free credits — skip payment entirely. Say something like "You've got a free card — who's it for?"

Step 6: Place the order

Confirm everything before submitting: recipient, address, front design, inside message, occasion. Mention it costs 1 credit and arrives in 5-7 business days. Only place when user says yes. Orders are irreversible.

Step 7: After the order

Confirm simply: "Done! [Name]'s card is on its way — about 5-7 business days."

Status translations: processing → "being made", in production → "being printed", shipped → "shipped! [tracking link]", delivered → "delivered!"

After a successful order, offer to save the contact info for next time (if the user hasn't already opted in): "Want me to remember [Name]'s details for next time?"

Local contacts database (opt-in)

If the user agrees to saving contacts, maintain ~/indexcards/birthdays.json as a local cache.

{"contacts": [{"name": "Kiall Wheatley", "birthday": "02-19", "relationship": "friend",
  "address": {"address1": "123 Main St", "city": "Springfield", "state": "IL", "zip": "62704", "country": "US"},
  "phone": "+15551234567", "notes": "Loves hiking. Prefers watercolor.",
  "cards_sent": [{"date": "2026-02-11", "occasion": "birthday", "style": "watercolor mountain", "message": "Happy birthday!", "order_id": "e5f67c35"}]}]}

Rules: MM-DD birthday format (no year). Don't duplicate — match on name. Update with every new piece of info. Append to cards_sent after every order. Cross-reference with GET /v1/orders/history to avoid duplicate suggestions.

Proactive suggestions (only if contacts database exists)

If ~/indexcards/birthdays.json exists (user previously opted in), at conversation start you may:

1. Check for birthdays/dates within 30 days, cross-ref with cards_sent
2. Check holidays — Mother's Day, Father's Day, Valentine's, Christmas, graduations
3. Review conversation history — hints like "my mom's been having a rough week"

Surface the 1-3 most timely suggestions naturally. Be specific ("Emma's birthday is Feb 28 — she loved the ink illustration last year"). Don't repeat suggestions the user already declined.

API Reference

Base URL: https://indexcards.com — all endpoints /v1/. Auth: Authorization: Bearer YOUR_API_KEY.

Register

POST /v1/auth/register
{"invite_code": "abc123def456"}  // optional — include if ?invite=CODE in URL

Returns: api_key, credits, free_generations_remaining (10 free), invite_credits. No email or password required — this is an anonymous registration. Store the returned api_key in the agent's secret store or session state for subsequent authenticated requests.

Generate Card Art

Option A (preferred): User's own Gemini key — if the user has a Gemini API key configured (e.g. GOOGLE_API_KEY or GEMINI_API_KEY env vars), use it directly for higher quality and no generation limits:

POST https://generativelanguage.googleapis.com/v1beta/models/imagen-4.0-generate-001:predict?key=USER_KEY
{"instances": [{"prompt": "YOUR PROMPT"}], "parameters": {"sampleCount": 1, "aspectRatio": "3:4"}}

Response: predictions[0].bytesBase64Encoded (base64 PNG). Save locally, upload via POST /v1/images/upload for a public URL.

Append to EVERY prompt when using Option A:

HARD CONSTRAINTS FOR THIS IMAGE:
- All artwork must be contained well within center with generous margins. Leave 15%+ blank space on every side.
- Pure white or very light background. No textures or gradients behind main subject.
- No borders, frames, rounded corners, or card mockup elements.
- Portrait orientation. No text unless explicitly requested.
- No digital artifacts. Clean, print-ready artwork.
- Must not look AI-generated. Aim for handmade: watercolor, linocut, gouache, ink, pencil, or collage.
- Centered composition with breathing room — will be printed on a physical card, edges may be trimmed.

Option B (fallback): Index Cards API — 10 free generations, then requires credits.

POST /v1/cards/generate
{"prompt": "...", "style": "watercolor", "reference_image_url": "https://...optional..."}

Returns: image_url, generation_id, free_generations_remaining, credits. Prompt constraints applied server-side.

Routing: Use Option A for text-to-image if Gemini key exists. Always use Option B for photo style transfer (reference_image_url) — Gemini can't do style transfer.

Validation: Min 600px short side, ~3:4 aspect ratio required. Ideal 1500×2100px. 422 on failure.

Preview

POST /v1/cards/preview
{"front_url": "...", "inside_url": "..."}

Returns: preview_url / video_url (MP4). Always generate after front + inside are approved.

Close-up

POST /v1/cards/closeup
{"image_url": "...", "label": "inside"}

Returns high-res JPEG. Use proactively when showing inside image so user can read text.

QR Code Composite

POST /v1/cards/qr/composite
{"card_image_url": "...", "url": "https://...", "position": "bottom-center", "size": "medium", "label": "Scan me!"}

Returns: image_url with QR overlaid. Use this URL as front_url/inside_url for ordering.

Standalone QR: POST /v1/cards/qr with {"url": "...", "size": "medium"}.

Credits

GET /v1/credits/check

Returns balance and Stripe payment links.

Place Order

POST /v1/orders
{"front_url": "...", "inside_url": "...", "recipient": {"name": "...", "address1": "...", "city": "...", "state": "...", "zip": "...", "country": "US", "phone": "+1..."}, "occasion": "birthday", "inside_message": "..."}

Required: front_url, inside_url, recipient.name, recipient.address1, recipient.city, recipient.zip, phone (recipient or sender). Optional: back_url, address2, state, country, occasion, inside_message, design_prompt, design_style. Costs 1 credit. Irreversible.

Other Endpoints

Error Codes

Data Handling & Privacy

What this skill stores locally

• API token: The Bearer token from /v1/auth/register should be stored in the agent's session state or secret store. It is an anonymous token (no email/password) used to authenticate API requests.
• Contacts cache (opt-in only): If the user agrees to saving contacts, ~/indexcards/birthdays.json stores names, birthdays, addresses, and card history. This file is user-visible and user-deletable. The agent only creates it after explicit user consent.

What this skill sends to the API

• Card artwork: Image URLs (hosted on indexcards.com after upload) for the card front and inside
• Recipient mailing address: Name, street address, city, state, ZIP, phone — required for physical mail delivery
• Occasion and message text: Used for order records only

What this skill does NOT do

• Does not read contacts, messages, calendar, or email without asking the user first
• Does not send contact data to the API — contact info is only cached locally (if user opts in) and used to pre-fill the address when sending a card
• Does not require or collect email addresses, passwords, or payment card numbers (payments happen via Stripe hosted checkout)

Payment flow

Credits are purchased via Stripe checkout. The skill sends the user a Stripe-hosted payment URL (returned by GET /v1/credits/check). No payment information passes through the skill or the Index Cards API. Invite codes grant free credits — no payment needed.

Homepage: https://indexcards.com