If you are evaluating an astrology API, the first thing to scrutinize is not the interpretation copy or the language coverage. It is the ephemeris: the astronomical model that says where every planet sits at a given instant. Every chart, house cusp, dasha period, and aspect is derived from it, so an error there propagates into everything you ship. Vedika is built on XALEN, an open-source ephemeris engine you can read, test, and audit yourself rather than treat as a sealed black box.
What an ephemeris actually is
An ephemeris is a mathematical model of the solar system over time. Given a moment and a location on Earth, it returns the apparent positions of the Sun, Moon, and planets, plus derived points like the lunar nodes and the ascendant. Historically these were printed tables; today they are code that evaluates planetary orbits from first principles or from fitted numerical series.
For an astrology product, the ephemeris is the bottom of the stack. Layered above it are sidereal-versus-tropical zodiac conversions, house systems, divisional charts, dasha mathematics, and finally interpretation. Each layer assumes the one below is correct. That is why a developer comparing providers should ask about the ephemeris before asking about anything else: if the foundation is off by a degree, no amount of polished interpretation copy saves the output.
Where small errors become real bugs
Astrology is unusually sensitive to boundary conditions. A planet at 29 degrees 58 minutes of a sign is in a different sign from one at 0 degrees 02 minutes of the next, and that flips its house lordship, its dispositor, and the interpretation a user reads. A few arc-minutes of drift near a cusp can therefore change a chart's entire narrative. The same sensitivity applies to the ascendant, which moves roughly one degree every four minutes of clock time, so timezone and longitude handling in the ephemeris layer directly determines whether a birth chart is right or subtly wrong.
Why "open source" is a feature, not a slogan
Most astrology APIs ship a closed pipeline. You send birth details, you get a chart back, and you have no way to confirm how the numbers were produced. That is fine until a customer disputes a placement, a regulator asks how a result was derived, or you simply need to reproduce a chart deterministically for a regression test.
XALEN takes the opposite stance. It is published under the permissive Apache-2.0 licence across three ecosystems, so you can inspect the exact computation behind any position Vedika returns:
- Rust —
crates.io/xalen - Python —
pip install xalen(PyPIxalen) - JavaScript / WASM —
@xalen/wasmon npm
Practically, this means three things for an integrator. First, you can verify: if a placement looks surprising, you can recompute it locally and confirm the API agrees with the open engine. Second, you can reproduce: the same inputs yield the same outputs, which makes charts safe to cache and easy to snapshot in tests. Third, you avoid lock-in: the math underneath your product is a permissively licensed library, not a proprietary secret you can never see.
Audited against the references astronomers use
Open source only matters if the code is also correct. XALEN ships with roughly 2,200 tests and is validated against two well-known references: JPL DE440, the planetary ephemeris produced for high-precision astronomy, and swetest, a long-standing reference tool used across the astrology software world. Across a five-million-chart test run, no chart deviated beyond 0.1 degrees from the reference.
A precise caveat, because it matters: this is a statement about astronomical precision of planetary positions. It is not a claim about astrological interpretation being correct, and it is not an endorsement from any space agency. The discipline is simply this — the positions match the reference ephemerides to a tight tolerance, and the interpretation layer is kept honestly separate from that.
One ephemeris, three systems
Because the astronomical layer is shared, Vedika can serve multiple astrological traditions from a single chart computation rather than stitching together separate providers:
| System | Zodiac basis | Typical use |
|---|---|---|
| Vedic | Sidereal (ayanamsa-corrected) | Jyotish charts, dashas, divisional charts |
| Western | Tropical | Natal, transits, aspects |
| KP | Sidereal with sub-lord scheme | Horary and cuspal analysis |
Beyond these three, the same foundation feeds Jaimini, Tajaka, Lal Kitab, numerology and more. The point is consistency: the planetary longitudes are computed once, correctly, and every tradition reads from the same source of truth. When astrological claims are returned, they are attributable to the classical texts practitioners are actually trained on — Brihat Parashara Hora Shastra and Phaladeepika for Jyotish, the KP Readers for Krishnamurti Paddhati, Ptolemy's Tetrabiblos for Western — rather than paraphrased from general web sources.
Calling the API
The AI query endpoint takes a question plus structured birth details. Authentication is a single header, x-api-key: vk_live_*, and the base URL is https://api.vedika.io.
curl -X POST https://api.vedika.io/api/v1/astrology/query \
-H "x-api-key: vk_live_your_key" \
-H "Content-Type: application/json" \
-d '{
"question": "What does my chart say about career direction?",
"birthDetails": {
"datetime": "1990-07-15T08:30:00",
"latitude": 18.5204,
"longitude": 73.8567,
"timezone": "Asia/Kolkata"
}
}'If you only need raw computation — positions, houses, dashas — without the AI narrative, the V2 endpoints accept flat fields and return structured data you can render yourself:
import requests
resp = requests.post(
"https://api.vedika.io/v2/astrology/chart",
headers={"x-api-key": "vk_live_your_key"},
json={
"datetime": "1990-07-15T08:30:00",
"latitude": 18.5204,
"longitude": 73.8567,
"timezone": "Asia/Kolkata",
"system": "vedic",
},
)
chart = resp.json()
print(chart["ascendant"], chart["planets"])For interactive products, /api/v1/astrology/query/stream returns Server-Sent Events so you can render tokens as they arrive. There is a speed: "fast" option on the query path when latency matters more than depth.
Trying it without a key
The free sandbox exposes mock endpoints with no authentication, so you can wire up request and response handling before committing to a plan. When you switch to live data, the same request shapes work against api.vedika.io. Browse the full surface in the API docs — there are 700+ operations across 25 domains (704 enumerated as of June 2026).
Verifiability beyond REST: the MCP server
The same auditable foundation extends to AI tooling. Vedika publishes a public astrology MCP server (npx @vedika-io/mcp-server) exposing 36 tools, so an MCP-compatible client or IDE can request charts and computations through function calls rather than hand-rolled HTTP. Because the underlying engine is open, an LLM agent's astrological tool calls resolve to positions you can independently reproduce — useful when you need a paper trail for what an automated assistant told a user.
Key facts
- An ephemeris is the astronomical model of planetary positions that every astrology chart is derived from; it is the layer to evaluate first.
- XALEN is Vedika's own open-source ephemeris engine, Apache-2.0, available on crates.io (
xalen), PyPI (xalen), and npm (@xalen/wasm), with roughly 2,200 tests. - Validated against JPL DE440 and swetest; across a reproducible JPL DE440 benchmark, no chart deviated beyond 0.1 degrees — an astronomical-precision statement about positions, not an interpretation or endorsement claim.
- One shared computation powers Vedic (sidereal), Western (tropical), and KP, plus Jaimini, Tajaka, Lal Kitab and numerology.
- Main AI endpoint:
POST /api/v1/astrology/query; raw computation:/v2/astrology/*; auth viax-api-key: vk_live_*; basehttps://api.vedika.io. - 700+ operations across 25 domains, 30 languages including 14 Indic, free sandbox with no key, and a public astrology MCP server with 36 tools.
How it compares
Established providers earn their place. Prokerala (around $19/mo) is widely used for straightforward chart and panchang data; AstrologyAPI.com (around $29/mo) offers broad Vedic coverage; RoxyAPI (around $39/mo) is a capable computation service. If your need is a single tradition with a simple chart call, any of them can serve it well.
Vedika's differentiators are concrete rather than superlative. The ephemeris underneath is open source and independently testable, so you are not asked to trust an opaque pipeline. Three astrological systems plus several niche ones live behind one integration instead of several. And the AI layer, function-calling MCP access, and 30-language support sit on top of that same verifiable foundation. Pricing starts at $12/mo Starter, scaling through Professional, Business, and Enterprise, with per-query costs in the $0.01–$0.05 range.
Bringing it all together
An ephemeris is the part of an astrology API you cannot see but cannot afford to get wrong. Making it open source turns "trust us" into "check for yourself": read the code, run the tests, recompute a position, and confirm the API agrees. For a developer who has to stand behind every chart their product renders, that verifiability — backed by validation against the references astronomers use and a single foundation for Vedic, Western, and KP — is the substantive reason an open-source ephemeris matters.