Eclipse Nexus Witness
Sales-tax determination witness for agent checkouts: sealed, vintage-stamped receipts (jurisdiction + rate + rule version at order time) an agent can attach to every order. LOCAL / fixture-vintage ONLY — fictional jurisdictions, DEMO rates, NOT tax advice, NOT real rates.
status: in-developmentclass: mcpTrust & ReceiptsCompliance & Regulation
Vendor: Cyan Eclipse Technologies
What it does
- Novel mechanism — the tax answer ships as a sealed, vintage-stamped witness receipt (jurisdiction + rate + rule version at order time), so a later audit replays the EXACT basis; tax APIs return answers, not evidence. verify_receipt replays the exact fixture rule at the receipt's vintage: a receipt whose rate doesn't match its vintage's rule is INVALID, and an old receipt keeps verifying against the OLD rule after a newer vintage is added.
- Forgery resistance benched, including the hard case: a receipt re-sealed so its own hash is self-consistent while claiming the new rate at the old vintage is still INVALID, because verification replays the fixture rule at the receipt's vintage instead of trusting the seal (bench forgery matrix 22/22).
- No bare-answer path exists: every determination ships a sealed receipt (receipt_hash + inputs_hash + rule version + vintage), and receipt_basis returns the exact rule record that produced it, resolved by the receipt's own vintage. Unknown jurisdiction, category, or vintage returns a clean refusal — no rate is invented, no latest-fallback, no fuzzy match.
- Honesty envelope by construction: every determination output carries demo_label 'DEMO — FIXTURE DATA — NOT TAX ADVICE — NOT REAL RATES', scope 'LOCAL / fixture-vintage ONLY', and source 'FIXTURE-DEMO'. The bundled table holds 13 rules across 5 fictional jurisdictions (Fixture Aurora/Boreal/Cascadia/Delta/Ember) — DEMO/fixture rates only, NOT tax advice, no live tax determination claim anywhere.
- Fix-before-live defects disclosed on the bench record (all LOW, none hidden): D1 the seal is an unkeyed local SHA-256 hash seal — VALID means consistent with the fixture rule at its vintage, not server-issued, and _verify does not assert the source/demo_label/scope constants; D2 refusal responses carry no DEMO envelope (no rate or advice is emitted on a refusal); D3 the advertised additionalProperties: false schemas are not enforced in dispatch (extra argument keys are silently ignored). D1 must be closed before any hosted/live scope.
- Python 3 standard library only; MCP over stdio; zero network calls and zero payment-processing code in the package (bench AST audit). Pricing is metadata only — paid access is via the Eclipse Bazaar bench-order path only; no checkout, payment, or buy-now surface exists.
Tools
determine · verify_receipt · list_rules · receipt_basis
Platforms
- MCP over stdio
Certification
Bench verdict: CERTIFIED (local, fixture-vintage)
Certified scope: CERTIFIED (local, fixture-vintage) — Verity independent bench 2026-10-26 (repo @ ec06f2e): 81/81 checks passed, two consecutive runs. Replay fidelity 11/11 (an old receipt verifies against the OLD fixture rule after a newer vintage is added; receipt id/hashes recomputed independently per SPEC §6); forgery matrix 22/22 (naive tamper INVALID on every field; re-sealed forgeries — including the new rate claimed at the old vintage — still INVALID, because verify_receipt replays the fixture rule at the receipt's vintage instead of trusting the seal); N-check 18/18 (no bare-answer path; unknown jurisdiction/category/vintage refuse cleanly and no rate is ever invented); honesty sweep 12/12 (DEMO envelope on every determination output; zero real-rate, tax-advice, or live-determination claims); hygiene 18/18 (zero network/payment code; exactly the 4 spec tools). Scope = LOCAL / fixture-vintage ONLY: local fixture lookup, stdio transport, bundled fictional fixture rates (13 rules, 5 fictional 'Fixture *' jurisdictions). DEMO rates only — NOT tax advice; no live tax determination is made by the product or tested here. Defects D1–D3 (all LOW) stand on the record as fix-before-live and are not hidden: D1 unkeyed seal (VALID means 'consistent with the fixture rule at its vintage', not 'issued by this server'; _verify does not assert source/demo_label/scope constants), D2 refusal responses carry no DEMO envelope, D3 advertised additionalProperties: false schemas not enforced in dispatch (extra argument keys silently ignored). Any live phase remains behind the SPEC §2 counsel gate (licensed data source + legal counsel review + explicit owner gate), and D1 must be closed before any hosted/live scope.
Not tested:
- Live tax determination — not in v0.1 by design: no real jurisdiction, real rate, tax-advice, or filing surface exists; any live phase remains behind the SPEC §2 counsel gate (licensed data source + legal counsel review + explicit owner gate) and is out of scope for this verdict
- Hosted or remote serving — v0.1 is local stdio only; bench defect D1 (unkeyed seal) must be closed before any hosted/live scope
- Server-issued authenticity — the seal is an unkeyed local SHA-256 hash seal, disclosed in SPEC §2/§6; VALID means 'consistent with the fixture rule at its vintage', not 'issued by this server' (bench defect D1)
Live state note: Bench evidence: argus-batch-20261026/bench/nexus-witness/VERDICT.md (Verity, independent bench over stdio JSON-RPC; rates and hashes recomputed independently from fixtures/rates.json + SPEC §6). This bench issued no test-bench/results scorecard; scorecard_ref is null and no scorecard is claimed or hosted for this product.
Pricing
PRICED — $0.25/check (PC-2) with sealed receipt, via the Eclipse Bazaar bench-order path only. No checkout, payment, or buy-now link exists for this product; v0.1 contains no payment, checkout, or billing code. Repository is PRIVATE (priced-product policy).
Install / verify
No install command is published for this product in the catalog or its registry record.
Official MCP Registry name: io.github.CYAN-ECLIPSE-TECHNOLOGIES-LLC/eclipse-nexus-witness-mcp
Registry listing: https://registry.modelcontextprotocol.io/v0.1/servers/io.github.CYAN-ECLIPSE-TECHNOLOGIES-LLC%2Feclipse-nexus-witness-mcp/versions/0.1.0
Repository: https://github.com/CYAN-ECLIPSE-TECHNOLOGIES-LLC/eclipse-nexus-witness-mcp
Verify any MCP server in your client configs against this catalog with bazaar check (Eclipse Bazaar MCP / CLI — see llms.txt).