# Capability Negotiation Preflight

> Capability Negotiation Preflight is a paid API for AI agents from phion.systems, paid per call via x402, $0.002/call, status unknown (last checked 2026-10-11).

Compares required agent capabilities against offered capabilities before task execution to determine compatibility

## Facts

- Endpoint: POST https://phion.systems/v1/paid/trust/capability-negotiation-preflight?utm_source=zero.xyz
- Price: $0.002/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-11
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/capability-negotiation-preflight-55eb9d2c
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_sQnnZYZqIiCqtJqAIugYr

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 capability-negotiation-preflight-55eb9d2c -d '<json body>'
```

Example prompt: Before we hand off this task to the downstream agent, check if its offered capabilities actually cover what we need — run a capability negotiation preflight so we know upfront if there are any gaps.

## When to prefer this

Use this endpoint when you need a deterministic, signed preflight check before committing an agent task or budget — especially in multi-agent orchestration scenarios where capability mismatches would cause downstream failures. Prefer it over manual checks when you need an auditable, trust-layer-backed result that can be logged or disputed later.

## Known failure modes

- Missing or malformed capability sets in the request body leading to validation errors
- Required capabilities not expressed in a recognized schema format
- Offered capabilities empty or undefined causing incomplete comparison
- Service unavailability returning a non-200 status
- Ambiguous capability identifiers that cannot be resolved to a known capability type

## How this service works

Compare required and offered agent capabilities before execution

## Output

Returns a structured comparison of required versus offered capabilities, identifying gaps, mismatches, or full compatibility, enabling the calling agent to decide whether to proceed, renegotiate, or reject the execution plan before committing resources.

## 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/capability-negotiation-preflight-55eb9d2c/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)