Headless Oracle | Signed Market-Status API for AI Agents

# Headless Oracle > Proposed reference implementation of environment.market_state — open as PR #9 on Mastercard's Verifiable Intent repo and filed as an IETF I-D for the environment.* family. > Ed25519-signed market-state attestations for 28 global exchanges. 60-second TTL. Fail-closed. > MCP server + REST API + x402 micropayments. Execution-environment verification for autonomous financial agents. At Layer 3 of a Verifiable Intent mandate, an agent holding a valid L2 credential still needs cryptographic proof that the market it is about to execute into is actually open. Amount validation at L2 is not evidence of market state at L3. Headless Oracle provides that evidence as a signed receipt. The environment.* constraint family is a sibling-type namespace: environment.market_state covers exchange-session state, and environment.wallet_state covers on-chain payment-source state. Both specs share the same fail-closed posture, JWKS caching discipline, cross-spec composition semantics, and family-wide register conventions — the result of coordinated drafting across sibling reference implementations rather than isolated per-type work. Model-agnostic infrastructure. Works with any AI agent regardless of model tier — from GPT-5 nano to frontier reasoning models like Anthropic Mythos. Receipts are the same $0.05/MTok agents and $125/MTok agents both consume. Regulatory alignment: Provides cryptographic venue-state attestation consistent with emerging regulatory direction on tokenized collateral and digital-asset derivatives (CFTC Staff Letter 25-39, Dec 2025; SEC Project Blueprint on Tokenized Collateral, Nov 2025). Final CFTC rulemaking expected Aug 2026. Agents can pay for access autonomously via x402 protocol (USDC on Base mainnet) — no human API key provisioning required. Headless Oracle returns cryptographically signed receipts confirming whether an exchange is OPEN, CLOSED, HALTED, or UNKNOWN. Every receipt includes an Ed25519 signature with a 60-second T

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