How readings get made.

What we are not doing

We are not predicting the future. We are not channeling. We are not claiming insight from elsewhere.

Tarot and astrology are symbolic systems— dense vocabularies for talking about parts of human experience that ordinary language handles badly. The card called The Tower is a useful name for the moment your life's scaffolding falls; the Moon in your 7th house is a useful name for "you find emotional safety through partnership." The reading is real in the way a metaphor is real.

What we do is take your input (a question, or a birth date+time+place) and have an AI produce a careful, personalized written reflection, framed in tarot or astrology's language. You can take it or leave it. The value is in what it surfaces for you, not in what it claims.

The AI model

Readings are generated by Anthropic's Claude (Sonnet 4.6 at the time of writing) — a large language model. We use Claude because its English prose is the most carefully measured among current frontier models, and because Anthropic offers zero-data-retention for API customers (your input is not used for training).

The system prompt is hand-tuned for each product:

• 3-card tarot:we send the 3 specific cards (upright/reversed), the user's question, and a prompt instructing Claude to interpret as journaling reflection across past/present/future.
• Birth chart: we first compute exact planetary positions, house cusps, and major aspects (Placidus, tropical) using circular-natal-horoscope-js, then feed Claude that geometry plus a system prompt for long-form interpretation.
• Compatibility (synastry): we compute both charts plus the cross-aspects between them, then ask Claude to read the dynamic — magnetic pulls, honest frictions, integration challenges.

Each reading uses one Claude API call, non-streaming, and takes about 30-40 seconds. We do not edit the output. We do not have human readers in the loop. What you receive is what Claude generated, end to end.

The tarot deck

Rider-Waite-Smith deck, 1909. Illustrated by Pamela Colman Smith under commission from A.E. Waite and published by William Rider & Son in London. It became the most influential tarot deck in English-language history, and nearly every modern deck (Wild Unknown, Modern Witch, Light Seer's) is built off RWS symbolism.

The artwork entered public domain in the U.S. decades ago, so we use Smith's original 1909 illustrations directly — not a paraphrased reinterpretation. Each card's symbolism is drawn from Waite's framework as documented in his 1910 Pictorial Key to the Tarot.

The astrology choices

Western tropical with Placidus houses. The default of nearly all modern English-language astrology apps — Co-Star, The Pattern, Sanctuary, Nebula — and what most people recognize as "their sign." We do not currently offer sidereal (Vedic) astrology.

See our astrology glossary for definitions of tropical vs. sidereal, Placidus vs. Whole Sign, and the major aspects.

Chart math uses the open-source circular-natal-horoscope-js library — a well-tested astronomical computation library, not a proprietary "magical" algorithm. You can verify our planetary positions against any other Placidus-based calculator.

What happens to your data

For free 3-card tarot readings: your question is sent to Claude, the reading streams back, and the data is gone. We do not store free-tier questions or readings.

For birth chart, compatibility, and year-ahead readings:

• Your birth data is used to calculate the chart and generate the reading in the current browser session.
• Anthropic receives your data for that one generation only, under their zero-data-retention agreement — they do not train models on it.

See our privacy policy for the full version.

Who we are

Tarot by Hand is a small, independent project. We are not affiliated with any larger astrology app or media company. We do not sell user data, run ads, or push a subscription. We make money one reading at a time, when readers choose to pay.

Questions, refund requests, partnerships: hello@tarotbyhand.com