xProof -- Prove Before & After Act — Accountability Layer for AI Agents

This skill enables your agent to anchor reasoning (WHY) on-chain before executing any significant action and the actual result (WHAT) after — creating a complete Prove Before & After Act cycle. Enforce pre-execution audit logging and detect violations via Base, producing tamper-proof, publicly verifiable records of who decided what, when, and why.

The Core Pattern: Prove Before & After Act

1. Reason (WHY) → 2. Hash locally → 3. Anchor WHY on-chain → 4. Get proof_id → 5. Execute → 6. Hash result (WHAT) → 7. Anchor WHAT on-chain → 8. Full 4W trail

Anchor reasoning (WHY) on-chain before execution. Anchor the actual result/output (WHAT) after for a complete 4W audit trail. The proof_id is your immutable pre-execution commitment — if something goes wrong, you have forensic evidence that the reasoning preceded the action.

4W breakdown — what each letter means and who provides it:

	Question	Provided by
WHO	Which agent or actor made this decision?	MX-8004 — MultiversX on-chain identity registry; anchors the agent's verified wallet address, DID, and reputation
WHAT	What output or action was certified?	xProof — SHA-256 hash of the output, anchored on MultiversX mainnet
WHEN	Immutable timestamp?	xProof — MultiversX block finality (~6 s); not a self-reported clock
WHY	What reasoning led to the decision?	xProof — action_description, risk_level, and context fields from /api/audit

xProof owns WHAT / WHEN / WHY and the causal link that proves reasoning preceded the action. MX-8004 owns WHO. Together they form a forensically complete 4W trail.

Agent reference: https://xproof.app/agent-context — 13 Q&A sections written specifically for autonomous agents: production deployment patterns, retry policy, x402 payment walkthrough, 4W audit trail deep-dive, privacy model, fleet monitoring, latency benchmarks, and framework integration examples (LangChain, CrewAI, AutoGen, LlamaIndex, OpenAI Agents SDK, Fetch.ai).

Why Prove Before Act? An agent that can prove its reasoning before acting is fundamentally more trustworthy than one that cannot. It creates an unbreakable causal chain: the intent existed before the action, and the blockchain makes that sequence immutable.

Why audit? Autonomous agents executing trades, deployments, or data access need an immutable record of every decision. The Agent Audit Log Standard enforces this: no proof = no execution.

Why violations? Trust requires accountability. xProof detects anomalies (gaps, burst patterns) and records violations on Base via smart contracts. Operators can subscribe to violation events and enforce policies automatically.

Pricing

Flat rate: $0.01 per proof -- no tiers, no volume discounts, same price whether you anchor 1 or 100,000 proofs.

Scale	Cost
1 proof	$0.01
1,000 proofs	$10
10,000 proofs	$100
50 agents × 20 actions/day × 30 days	$300/month

Payment: USDC on Base (x402, no account) or EGLD on MultiversX (ACP/wallet) or prepaid credits.

Quick Install

The canonical source for all skill files is the main xProof repository (jasonxkensei/xProof), which is the repository audited by security tools. Install from there directly:

mkdir -p .agent/skills/xproof/references

# Core Skill — from the canonical main repository
curl -sL https://raw.githubusercontent.com/jasonxkensei/xProof/main/clawhub-publish/xproof/SKILL.md \
  > .agent/skills/xproof/SKILL.md

# Reference Manuals
for f in certification x402 mcp; do
  curl -sL "https://raw.githubusercontent.com/jasonxkensei/xProof/main/clawhub-publish/xproof/references/${f}.md" \
    > ".agent/skills/xproof/references/${f}.md"
done

Source verification: All files above are served from github.com/jasonxkensei/xProof — the same repository that contains the server code, contracts, and SDKs. You can audit the full source at that URL before installing.

Security

• NEVER commit API keys to a public repository.
• ALWAYS add .env to your .gitignore.
• API keys are prefixed pm_ -- treat them like passwords.
• x402 mode requires no API key (payment replaces authentication).
• NEVER send plaintext content to xproof.app -- always hash locally first (sha256sum, crypto.subtle.digest, or equivalent). The only field xproof accepts is file_hash (64-char SHA-256 hex). No raw text, documents, or binary data should ever leave your environment.
• x402 is opt-in and autonomous -- once enabled, your agent can initiate USDC payments on Base without per-transaction confirmation. Configure a spending cap in your agent framework and require human approval above your threshold before enabling x402 in production.
• llms.txt and llms-full.txt are static documentation references -- load them once at install time for API reference, not at runtime on every call. Fetching them dynamically on each invocation creates an unnecessary runtime dependency on xproof.app availability and a potential prompt-injection surface if the file is ever compromised.
• Guard/enforcement templates are versioned in the repository -- never fetch agent enforcement code from a runtime URL. Use the pinned versions in references/ or the SDK packages (xproof on PyPI, @xproof/xproof on npm).

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Configuration

Option A: API Key Authentication

# ---- xProof ---------------------------------------------------------------
XPROOF_API_KEY="pm_..."                          # Your API key (from xproof.app)
XPROOF_BASE_URL="https://xproof.app"             # Production endpoint

Get an API key at xproof.app (connect wallet, go to Settings > API Keys).

Option B: x402 Payment Protocol (No Account Required)

No configuration needed. Pay in USDC on Base (eip155:8453) directly in the HTTP request. The 402 response header tells your agent exactly what to pay. Flat rate: $0.01 per proof.

WARNING -- autonomous payments: x402 is an opt-in mode that enables your agent to initiate on-chain USDC transactions without per-transaction user confirmation. Before enabling x402 in production:

• Set a spending cap in your agent framework (e.g. max $N/day or $N/session).
• Require human approval for any single call that would exceed your risk threshold.
• Note that POST /api/batch supports up to 100 items per call -- at $0.01 each, a batch of 100 costs $1.00.
• Disable x402 entirely in environments where autonomous spending is not authorised.

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1. Core Skills Catalog

1.1 Proof Anchoring (REST API)

Full Reference

Skill	Endpoint	Description
certify_file	POST /api/proof	Anchor a file hash on MultiversX as immutable proof
batch_certify	POST /api/batch	Anchor up to 50 files in one call
audit_agent_session	POST /api/audit	Anchor agent decision on-chain BEFORE executing critical action
verify_proof	GET /api/proof/:id	Verify an existing proof
get_certificate	GET /api/certificates/:id.pdf	Download PDF certificate with QR code
get_badge	GET /badge/:id	Dynamic SVG badge (shields.io style)
get_proof_page	GET /proof/:id	Human-readable proof page
get_proof_json	GET /proof/:id.json	Structured proof document (JSON)
get_audit_page	GET /audit/:id	Human-readable audit log page

1.2 Proof Anchoring (MCP -- JSON-RPC 2.0)

Full Reference

Tool	Description
certify_file	Create blockchain proof -- SHA-256 hash, filename, optional author/webhook
verify_proof	Verify existing proof by UUID
get_proof	Retrieve proof in JSON or Markdown format
discover_services	List capabilities, pricing, and usage guidance
audit_agent_session	Anchor agent decision on-chain BEFORE executing critical action

1.3 Payment (x402)

Full Reference

x402 is not a separate skill -- it is a payment method. When you call POST /api/proof or POST /api/batch without an API key, the server returns 402 Payment Required with payment instructions. Your agent pays in USDC on Base and retries with an X-Payment header.

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2. Coherence Loop — close the WHY→WHAT link

Anchoring the WHY and the WHAT is not enough: you must link them. An unlinked WHY anchor shows as divergent in your public coherence history after 1 hour, and after the 2-hour TTL it is additionally flagged as a proposed fault violation — both lower your public coherence rate.

Full loop: check_coherence (WHY) → execute → certify_file with metadata.why_proof_id (WHAT) → POST /api/coherence/link.

# Step 4 — close the loop (API key required; both proofs must be yours)
curl -X POST https://xproof.app/api/coherence/link \
  -H "Authorization: Bearer pm_..." \
  -H "Content-Type: application/json" \
  -d '{"why_proof_id": "<UUID from check_coherence>", "what_proof_id": "<UUID from certify_file>"}'
# → 200 {"success": true, "coherence_check": {"coherence_score": 85, ...},
#        "score_breakdown": {"linked": true, "what_within_1h": true,
#                            "what_references_why": true, "what_confirmed_on_chain": false,
#                            "execution_preceded_intent": false}}

Score (0–100): 50 for linking + 15 if WHAT within 1h of WHY + 20 if WHAT's metadata.why_proof_id references the WHY + 15 if WHAT confirmed on-chain. WHAT certified before the WHY → base halved to 25.

Error cases:

Status	Error	Meaning
409	ALREADY_LINKED	WHY anchor already linked to a different WHAT. Re-linking the same pair returns 200 with already_linked: true (idempotent).
400	NOT_A_COHERENCE_ANCHOR	why_proof_id is a regular proof. Create the WHY via the check_coherence MCP tool, or certify with metadata.type = "coherence_check".
404	WHY_PROOF_NOT_FOUND / WHAT_PROOF_NOT_FOUND	Proof missing or owned by another account.

SDK helpers: client.link_coherence(why_proof_id, what_proof_id) (Python xproof ≥ 0.2.10) · client.linkCoherence(whyProofId, whatProofId) (npm @xproof/xproof ≥ 0.1.11).

Check your history: GET https://xproof.app/api/agents/<wallet>/coherence — public; per-anchor status (linked / pending / divergent) + aggregate coherence rate.

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3. Webhooks

Supply an optional webhook_url field on POST /api/proof or POST /api/batch to receive a callback when the proof is confirmed on-chain.

Scope — the webhook payload contains only:

Field	Type	Description
proof_id	string (UUID)	The proof identifier
file_hash	string	SHA-256 hex of the certified file
filename	string	Filename submitted with the proof
status	string	"confirmed"
blockchain_tx	string	MultiversX transaction hash
explorer_url	string	Link to the transaction on MultiversX Explorer
timestamp	string	ISO 8601 confirmation time

No raw file content, no API keys, no account information, and no metadata beyond the above is ever sent to the webhook endpoint.

Authentication: Every delivery includes an X-Webhook-Signature header containing an HMAC-SHA256 signature computed with a per-relationship secret. Verify this signature before processing the payload. Retry policy: 3 attempts with exponential backoff (1 s, 5 s, 30 s).

SSRF protection: xproof.app validates webhook_url before delivery. Private IP ranges (RFC 1918), loopback (127.x, ::1), link-local, and non-HTTPS destinations are blocked. DNS rebinding is mitigated by pinning the resolved socket address to the pre-validated IP at connection time.

# Example proof request with webhook
curl -X POST https://xproof.app/api/proof \
  -H "Authorization: Bearer pm_..." \
  -H "Content-Type: application/json" \
  -d '{
    "file_hash": "a1b2c3...",
    "filename": "output.json",
    "webhook_url": "https://your-agent.example.com/hooks/xproof"
  }'

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9. Violations Layer (Base)

xProof monitors agent behavior and detects anomalies. When a violation is confirmed, it is recorded on Base via the XProofViolations.sol smart contract, impacting the agent's trust score.

Violation Types

Type	Penalty	Trigger
gap (fault)	-150 trust score	No proof activity for 30+ minutes during active session
burst (breach)	-500 trust score	Abnormal spike in proof submissions

Smart contracts: XProofViolations.sol | ViolationWatcher.sol

Docs: https://xproof.app/docs/base-violations

---

10. Agent Proof Standard

xProof implements the open Agent Proof Standard -- a composable, chain-agnostic format for agent accountability.

Full specification: AGENT_PROOF_STANDARD.md

Standard API: GET /api/standard | GET /api/standard/validate (POST)

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11. Discovery Endpoints

Endpoint	Description
GET /.well-known/agent.json	Agent Protocol manifest
GET /.well-known/mcp.json	MCP server manifest
GET /.well-known/agent-audit-schema.json	Agent Audit Log canonical schema
GET /ai-plugin.json	OpenAI ChatGPT plugin manifest
GET /llms.txt	LLM-friendly summary
GET /llms-full.txt	Complete LLM reference
POST /mcp	MCP JSON-RPC 2.0 endpoint
GET /mcp	MCP capability discovery
GET /api/standard	Agent Proof Standard specification
GET /agent-context	Agent-first deep-dive: production patterns, retry policy, 4W walkthrough, x402, cost, MCP examples, framework integrations

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12. Command Cheatsheet

# Hash locally first -- the original content must never leave your environment.
# xproof only receives the SHA-256 hex hash, filename, and metadata you choose to share.
sha256sum myfile.pdf | awk '{print $1}'
# Then POST the hash to /api/proof

# Anchor via MCP
curl -X POST https://xproof.app/mcp \
  -H "Authorization: Bearer pm_..." \
  -d '{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"certify_file","arguments":{"file_hash":"...","filename":"myfile.pdf"}}}'

# Verify a proof
curl https://xproof.app/api/proof/<proof_id>

# Get badge (embed in README)
![xProof](https://xproof.app/badge/<proof_id>)

# Batch anchor
curl -X POST https://xproof.app/api/batch \
  -H "Authorization: Bearer pm_..." \
  -d '{"files":[{"file_hash":"...","filename":"a.txt"},{"file_hash":"...","filename":"b.txt"}]}'

# Close the WHY→WHAT coherence loop (after check_coherence + certify_file)
curl -X POST https://xproof.app/api/coherence/link \
  -H "Authorization: Bearer pm_..." \
  -d '{"why_proof_id":"<why-uuid>","what_proof_id":"<what-uuid>"}'

# Health check
curl https://xproof.app/api/acp/health