# Touchstone Assay — Dated SIU

Dated SIU is the benchmark price of AI inference work: a versioned basket of
inference tasks, executed against real provider APIs and priced against a
signed, dated print — measured by actually buying inference, not by surveying
list prices. One SIU (Standard Inference Unit) is a fixed quantity of that
work; the print is the dollar price of one basket.

TESTBED — Base Sepolia. Real signed prints, real settlements on a test
network. Not mainnet, not traction.

## For agents

MCP server (Streamable HTTP): https://mcp.touchstoneassay.com/mcp
Machine-readable config + pricing: https://touchstoneassay.com/mcp.json
Human page: https://touchstoneassay.com/for-agents.html

Four tools. `get_index` is free. The other three are paid per call via x402
(Circle Gateway nanopayments), settled in USDC on Base Sepolia
(`eip155:84532`):

- `get_index(version?, date?)` — free — returns the current signed print.
- `get_quote(task_class, model)` — $0.001 — SIU price and USD equivalent for
  one call of a given task class against a given model.
- `convert(model, input_tokens, output_tokens)` — $0.001 — SIU + USD
  equivalent for a specific token count.
- `verify_receipt(chain, tx_hash)` — $0.01 — reads an on-chain settlement and
  returns a signed attestation of what was quoted versus what was actually
  paid.

## For humans and other crawlers

Site: https://touchstoneassay.com
Methodology: https://touchstoneassay.com (see "Methodology" — the full
computation rules, quality gates, and registry policy)
Source: https://github.com/petrkrulis2022/dated-siu-inference

Never "backed by," never a peg, never an oracle, never for sale. Touchstone
Assay publishes a measurement, not an instrument.