# Sybil Reputation Guard

> Sybil Reputation Guard is a paid API for AI agents from phion.systems, paid per call via x402, $0.004/call, status unknown (last checked 2026-10-22).

Assesses multiple manipulation signals to produce a sybil/bot reputation score with uncertainty quantification and mandatory abstention when confidence is insufficient

## Facts

- Endpoint: POST https://phion.systems/v1/paid/trust/sybil-reputation-guard?utm_source=zero.xyz
- Price: $0.004/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-22
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/sybil-reputation-guard-db4b683a
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_ztPqTTscmRlPY6SqsLm2r

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

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability sybil-reputation-guard-db4b683a -d '<json body>'
```

Example prompt: Before I proceed with this agent's request, can you run a sybil reputation check on it — assess all manipulation signals and let me know if the result is uncertain enough that you'd recommend abstaining rather than trusting it?

## When to prefer this

Choose this endpoint when you need a nuanced, uncertainty-aware sybil and manipulation assessment rather than a binary pass/fail — particularly when abstention is a safe and required option (e.g., before payments, task handoffs, or granting access). Prefer it over generic fraud-detection APIs when the subject is an AI agent or autonomous system, and when you need explicit confidence signaling so downstream logic can safely defer action under ambiguity.

## Known failure modes

- Insufficient signal data may trigger mandatory abstention rather than a score
- Ambiguous or sparse behavioral metadata may result in high uncertainty output
- Malformed or missing input entities may return a validation error
- Novel manipulation tactics not covered by current signal set may evade detection
- Rate limits or payment failures may prevent the call from completing

## How this service works

Assess multiple manipulation signals with uncertainty and mandatory abstention

## Output

Returns a structured assessment of multiple manipulation signals, a reputation score for the evaluated entity, an uncertainty estimate indicating confidence in the verdict, and a mandatory abstention flag when the evidence is insufficient to make a reliable determination — allowing the calling agent to decide whether to proceed or hold.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input",
  "output"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "body"
   ],
   "properties": {
    "body": {
     "type": "object",
     "additionalProperties": true
    }
   }
  },
  "output": {
   "type": "object",
   "required": [
    "example"
   ],
   "properties": {
    "example": {
     "type": "object",
     "additionalProperties": true
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json"
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/sybil-reputation-guard-db4b683a/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from phion.systems](https://www.zero.xyz/host/phion.systems/llms.txt)