Aethis SDK for Python

Official Python SDK for the Aethis developer API — eligibility decisions, ruleset schemas, and stateful decision sessions.

Documentation: docs.aethis.ai · OpenAPI spec · agents via MCP: claude mcp add aethis -- npx -y aethis-mcp

Authoring is in private beta. Decision endpoints are public — Aethis() works with no key. Authoring endpoints require an invite. The CLI (aethis-cli) is the supported authoring path during the beta — see docs.aethis.ai/recipes/author-a-rule for the test-driven workflow (rulesets cannot publish with a failing test). Request access at aethis.ai/developer-access.

Install

uv add aethis-sdk

# Or, for a standalone venv:
uv pip install aethis-sdk

Python 3.11+. Requires httpx and pydantic. SDK v0.5.0+ ships the composed-rulebook decision surface (decide_rulebook) and rulebook_id on DecideResponse.

Quickstart

Examples below target aethis/uk-fsm/child-eligibility — a live public ruleset (UK Free School Meals, child-eligibility section). Browse all live rulesets with curl https://api.aethis.ai/api/v1/public/rulesets.

Single-ruleset decision endpoints are anonymous on public rulesets — Aethis() works with no key. Composed-rulebook decisions (decide_rulebook) and authoring endpoints require an API key. Pass api_key="ak_live_..." to Aethis(...) for those paths.

One-shot decision (sync)

from aethis_sdk import Aethis

with Aethis() as client:
    response = client.decide(
        ruleset_id="aethis/uk-fsm/child-eligibility",
        field_values={
            "child.age": 10,
            "child.school_type": "state_funded",
        },
    )
    print(response.decision)        # "eligible" | "not_eligible" | "undetermined"
    print(response.inputs_hash)     # canonical SHA-256 fingerprint of the input set
    print(response.decision_id)     # per-call audit identifier
    print(response.engine_version)  # e.g. "aethis-core@0.27.0"

The four audit fields above (inputs_hash, decision_id, decision_time, engine_version) ship in 0.3.2+. Same inputs_hash always produces the same outcome from the same engine_version — store these alongside the decision for a defensible audit trail.

One-shot decision (async)

import asyncio
from aethis_sdk import AsyncAethis

async def main():
    async with AsyncAethis() as client:
        response = await client.decide(
            ruleset_id="aethis/uk-fsm/child-eligibility",
            field_values={"child.age": 10, "child.school_type": "state_funded"},
        )
        print(response.decision)

asyncio.run(main())

Composed rulebook (requires API key — v0.5.0+)

A Rulebook composes multiple rulesets via an outcome_logic expression — e.g. UK FSM's child_eligibility AND (household_criteria OR universal_infant). Hit the whole-form decision with decide_rulebook:

from aethis_sdk import Aethis

with Aethis(api_key="ak_live_...") as client:
    response = client.decide_rulebook(
        rulebook_id="aethis/uk-fsm",
        field_values={
            "child.age": 10, "child.year_group": "year_6",
            "child.school_type": "state_funded",
            "household.receives_universal_credit": True,
            "household.annual_net_earnings": 5000,
            "household.receives_income_support": False,
            "household.receives_income_based_jsa": False,
            "household.receives_income_related_esa": False,
            "household.receives_child_tax_credit_only": False,
            "household.receives_nass_support": False,
            "child.is_looked_after": False,
            "child.is_care_leaver": False,
        },
    )
    print(response.decision)      # "eligible"
    print(response.rulebook_id)   # "rb_kzZ_td0tbKW_OLRB" (slug resolved)

Rulebook decide is always scope-gated by the engine — anonymous callers get HTTP 401, regardless of rulebook visibility. The decide_rulebook method and the rulebook_id field on DecideResponse ship in SDK v0.5.0. AsyncAethis.decide_rulebook(...) is the async equivalent.

Stateful decision session

Accumulate answers locally and query the API only when needed. Cached until an answer changes. The session does not manage the client — the caller keeps the Aethis context open for the session's lifetime.

from aethis_sdk import Aethis, SyncDecisionSession

RULESET_ID = "aethis/uk-fsm/child-eligibility"

with Aethis() as client:
    schema = client.get_schema(RULESET_ID)
    session = SyncDecisionSession(RULESET_ID, client, schema)
    session.answer("child.school_type", "state_funded")
    while (nq := session.next_question()) is not None:
        answer = input(f"{nq.question} ")
        session.answer(nq.field_id, answer)
    print("Eligible:", session.is_eligible())

Note: input() returns a string. For non-string fields (int / bool / enum) coerce the answer before calling session.answer() — the API expects the typed value.

Authoring (requires a key)

with Aethis(api_key="ak_live_...") as client:
    # ruleset publishing endpoints — see the Aethis CLI for the
    # full authoring workflow:
    # https://github.com/Aethis-ai/aethis-cli
    ...

The async equivalent is DecisionSession — same surface, await on the HTTP methods (decide, is_eligible, next_question, status).

What's included

Configuration

• api_key — optional during the developer beta for evaluation endpoints (/decide, /schema, /explain, /source). Required for authoring endpoints (publishing rulesets, etc.). Provisioned via aethis.ai.
• base_url — defaults to https://api.aethis.ai. HTTP is only permitted for localhost / 127.0.0.1 or when passing a test transport.
• timeout — per-request, seconds. Defaults to 5.
• iam_token — optional bearer token for Cloud Run service-to-service auth.

Status

Pre-1.0. The decision surface (/decide, /schema) is stable; authoring endpoints (projects, rulesets, publishing) are not yet exposed here — use the Aethis CLI for those.

Links

• Issue tracker: https://github.com/Aethis-ai/aethis-sdk-python/issues
• API docs: https://aethis.ai