# Services from phion.systems on Zero

> phion.systems serves 47 paid API services for AI agents, indexed by Zero. Each is callable per call with payment handled by Zero.

Canonical page: https://www.zero.xyz/host/phion.systems
Live health (JSON, refreshed every minute): https://www.zero.xyz/host/phion.systems/health.json

## Services

- [MCP Manifest Firewall](https://www.zero.xyz/c/mcp-manifest-firewall-0a0baf42/llms.txt): $0.002/call via x402. Inspects an MCP tool manifest for security and quality issues including tool name collisions, missing schemas, and prompt injection attacks before installation or trust
- [Phion Systems Web Evidence Fetcher](https://www.zero.xyz/c/phion-systems-web-evidence-fetcher-4040da74/llms.txt): $0.004/call via x402. Fetches web content as cryptographically hashed and signed evidence, screened against prompt injection, for use by AI agents
- [Human Approval Policy](https://www.zero.xyz/c/human-approval-policy-319ec7a6/llms.txt): $0.002/call via x402. Determines whether an agent action should be allowed to run immediately, held for human approval, or denied outright based on policy rules
- [Phion Attest – Signed Integrity & Provenance Receipt for AI-Agent JSON](https://www.zero.xyz/c/phion-attest-signed-integrity-provenance-receipt-for-ai-agent-json-239932fc/llms.txt): $0.001/call via x402. Issues a signed, hash-linked receipt attesting to the integrity, provenance, and freshness of AI-agent JSON payloads
- [phion.systems Preflight Payment Firewall](https://www.zero.xyz/c/phion-systems-preflight-payment-firewall-c7e08039/llms.txt): $0.002/call via x402. Runs a deterministic payment-policy check before an agent executes a payment, returning a signed, short-lived decision receipt authorizing or blocking the transaction.
- [Redirect Callback Validator](https://www.zero.xyz/c/redirect-callback-validator-4b7ed8a5/llms.txt): $0.002/call via x402. Validates HTTPS callback and redirect destination URLs against an explicit host allowlist to prevent open redirect and SSRF attacks
- [Phion Agent Inspector](https://www.zero.xyz/c/phion-agent-inspector-24bddb06/llms.txt): $0.009/call via x402. Runs independent due diligence on an AI-agent service endpoint, checking x402, A2A, MCP, OpenAPI, ERC-8004, reachability, and returning signed evidence
- [Phion Agent Commerce Journey Verifier](https://www.zero.xyz/c/phion-agent-commerce-journey-verifier-015349f6/llms.txt): $0.01/call via x402. Verifies a hash-linked agent commerce journey and issues a signed portable receipt proving the chain of events occurred as claimed
- [Delegation Scope Guard](https://www.zero.xyz/c/delegation-scope-guard-254d663a/llms.txt): $0.003/call via x402. Validates least-privilege capabilities, data scope, destinations, budget, and expiry constraints before one agent delegates to another agent
- [Memory Write Guard](https://www.zero.xyz/c/memory-write-guard-efe4a0f1/llms.txt): $0.002/call via x402. Screens proposed persistent agent-memory writes for poisoning attempts, missing provenance, secret leakage, and unsafe instructions before committing them
- [Tool Capability Drift Monitor](https://www.zero.xyz/c/tool-capability-drift-monitor-b4065b4a/llms.txt): $0.002/call via x402. Detects and reports changes between a trusted baseline snapshot of a tool's capabilities and its current live manifest
- [Agent Budget Guard](https://www.zero.xyz/c/agent-budget-guard-ad326b74/llms.txt): $0.002/call via x402. Enforce declared per-call, task, session, and period spending budgets before an agent executes a paid action
- [Agent Task Handoff Receipt](https://www.zero.xyz/c/agent-task-handoff-receipt-5058c808/llms.txt): $0.003/call via x402. Validates and cryptographically signs a portable task handoff packet including scope, budget, and expiry for secure agent-to-agent delegation
- [Dependency Provenance Assessment](https://www.zero.xyz/c/dependency-provenance-assessment-4d431928/llms.txt): $0.003/call via x402. Checks declared software dependencies for identity integrity, source authenticity, and cryptographic digest coverage
- [Domain Ownership Evidence](https://www.zero.xyz/c/domain-ownership-evidence-a09304d1/llms.txt): $0.003/call via x402. Attests DNS and HTTPS domain-control proof status, producing signed evidence that a declared domain is under the caller's control
- [Inter-Agent Policy Evaluator](https://www.zero.xyz/c/inter-agent-policy-evaluator-9382d2be/llms.txt): $0.003/call via x402. Detects compatibility or conflicts between two or more agent policies to prevent unsafe or contradictory agent-to-agent interactions
- [Manifest Version Diff](https://www.zero.xyz/c/manifest-version-diff-10a27d4c/llms.txt): $0.002/call via x402. Identifies changed fields and hashes between two versions of an agent or software manifest
- [Payment Route Selector](https://www.zero.xyz/c/payment-route-selector-e02293ef/llms.txt): $0.002/call via x402. Rejects impossible or unsafe x402 payment routes, ranks eligible routes by policy, and returns a directly executable next payment action
- [Secret Redaction Preflight](https://www.zero.xyz/c/secret-redaction-preflight-054be188/llms.txt): $0.002/call via x402. Detects and redacts common secret indicators (API keys, tokens, passwords, credentials) from a payload before it is transmitted to an external tool or service.
- [Tool Call Policy Guard](https://www.zero.xyz/c/tool-call-policy-guard-74da6a67/llms.txt): $0.002/call via x402. Validates a proposed tool call against declared intent, allowed tools, permitted destinations, and cost limits before allowing execution
- [Tool Output Firewall](https://www.zero.xyz/c/tool-output-firewall-485d79d1/llms.txt): $0.002/call via x402. Inspects and validates untrusted tool output before it enters an agent context or triggers a downstream action
- [PHION Transaction Recovery](https://www.zero.xyz/c/phion-transaction-recovery-159e1518/llms.txt): $0.01/call via x402. Classifies a failed agent transaction and produces a signed, machine-readable recovery claim with a deterministic remedy plan
- [Abandoned Tool Detector](https://www.zero.xyz/c/abandoned-tool-detector-71e4c467/llms.txt): $0.003/call via x402. Assesses whether an AI agent tool or external service is still reachable and whether its observations are fresh or stale
- [Data Egress Preflight](https://www.zero.xyz/c/data-egress-preflight-5cbd59f6/llms.txt): $0.002/call via x402. Inspects outbound agent payloads for secrets, unsafe destinations, and size limits before they are sent to an external tool or API
- [Webhook Verifier](https://www.zero.xyz/c/webhook-verifier-19174f75/llms.txt): $0.003/call via x402. Validates the signature status, freshness, and payload evidence of incoming webhooks to confirm authenticity and integrity
- [Conflict Resolution](https://www.zero.xyz/c/conflict-resolution-c416d811/llms.txt): $0.003/call via x402. Selects among conflicting agent results using explicit, policy-driven arbitration to resolve ambiguity
- [Data Freshness Certificate](https://www.zero.xyz/c/data-freshness-certificate-cfc7f68e/llms.txt): $0.002/call via x402. Calculate data age against an explicit freshness policy and return a certificate indicating whether the data meets freshness requirements
- [Duplicate Charge Detector](https://www.zero.xyz/c/duplicate-charge-detector-f80a7530/llms.txt): $0.003/call via x402. Detects duplicate charge fingerprints to prevent double-billing in agent payment flows
- [Idempotency Replay Guard](https://www.zero.xyz/c/idempotency-replay-guard-01f1945a/llms.txt): $0.002/call via x402. Detects whether reuse of an idempotency key is a safe replay of a prior request or a conflicting misuse that should be rejected
- [OAuth Token Audience Guard](https://www.zero.xyz/c/oauth-token-audience-guard-8a893904/llms.txt): $0.002/call via x402. Verifies a JWT or OAuth token's declared audience (aud) and issuer (iss) claims after local cryptographic signature validation has already been performed
- [Purpose-Bound Consent](https://www.zero.xyz/c/purpose-bound-consent-6262af1c/llms.txt): $0.003/call via x402. Binds declared user or agent consent to a specific action purpose, scope, and expiry window, creating a verifiable consent record
- [Signed Result Comparator](https://www.zero.xyz/c/signed-result-comparator-d0065da1/llms.txt): $0.003/call via x402. Compares multiple agent results and produces a cryptographically signed record of exact agreement or conflict evidence between them
- [Context Provenance Labeler](https://www.zero.xyz/c/context-provenance-labeler-6d80bf99/llms.txt): $0.002/call via x402. Hashes and labels agent context with integrity, confidentiality, and source declarations to establish trust provenance
- [Delivery Evidence](https://www.zero.xyz/c/delivery-evidence-d8db02f2/llms.txt): $0.003/call via x402. Hashes and cryptographically attests supplied delivery evidence for tamper-proof verification
- [PHION Mandate Capacity Reservation](https://www.zero.xyz/c/phion-mandate-capacity-reservation-a7db0495/llms.txt): $0.004/call via x402. Atomically reserves cumulative mandate capacity and returns a signed state receipt for AI-agent payment mandate workflows
- [Portable Observability Audit](https://www.zero.xyz/c/portable-observability-audit-59dc59fc/llms.txt): $0.004/call via x402. Validates and cryptographically signs a portable event hash chain to establish tamper-evident audit trails for agent activity
- [Service SLA Attestation](https://www.zero.xyz/c/service-sla-attestation-eec7b043/llms.txt): $0.004/call via x402. Calculates and cryptographically signs availability and latency evidence derived from bounded samples to produce verifiable SLA attestations
- [Interrupted Task Recovery](https://www.zero.xyz/c/interrupted-task-recovery-06467025/llms.txt): $0.003/call via x402. Plans bounded, idempotent resumption of an agent task from a checkpoint after interruption
- [MCP Server Identity Evidence](https://www.zero.xyz/c/mcp-server-identity-evidence-095a564a/llms.txt): $0.003/call via x402. Creates signed cryptographic evidence binding an MCP server's declared domain, endpoint, manifest, public key, and version together into a verifiable identity attestation
- [PHION Execute](https://www.zero.xyz/c/phion-execute-0706147c/llms.txt): $0.001/call via x402. Execute any selected PHION service with a budget cap, persistent idempotency, acceptance checks, and a signed completion envelope
- [Resource Cycle Guard](https://www.zero.xyz/c/resource-cycle-guard-ff108104/llms.txt): $0.002/call via x402. Detects and stops repeated execution cycles and step count overruns in AI agent workflows
- [Retention & Deletion Receipt](https://www.zero.xyz/c/retention-deletion-receipt-55b6906c/llms.txt): $0.003/call via x402. Signs and records a declared data retention or deletion action to produce a verifiable compliance receipt
- [PHION Schema Normalize & Repair](https://www.zero.xyz/c/phion-schema-normalize-repair-e0a6a9d2/llms.txt): $0.001/call via x402. Normalizes an agent payload to a PHION service schema without altering payment-critical values, returning a signed repair receipt
- [Subscription Spend Guard](https://www.zero.xyz/c/subscription-spend-guard-b9bc9b0a/llms.txt): $0.003/call via x402. Enforces recurring period budgets for agent subscriptions, blocking spend that exceeds defined limits within a billing cycle
- [x402 Quote Comparator](https://www.zero.xyz/c/x402-quote-comparator-9b066344/llms.txt): $0.002/call via x402. Normalizes and compares multiple x402 payment quotes to help agents select the best route or validate consistency across providers
- [Concurrency Guard](https://www.zero.xyz/c/concurrency-guard-cdd4d8bd/llms.txt): $0.002/call via x402. Enforces concurrent execution slot limits to prevent agents or workflows from exceeding defined parallelism thresholds
- [Payment Receipt Reconciler](https://www.zero.xyz/c/payment-receipt-reconciler-52b0b188/llms.txt): $0.003/call via x402. Reconciles payment and receipt fields to verify that payment records match corresponding receipt data

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

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