# Vault Key Existence Check

> Vault Key Existence Check is a paid API for AI agents from agentic-endpoints-testnet.oliver-835.workers.dev, paid per call via x402, $0.001/call, status unknown (last checked 2026-09-14).

Checks whether a specific key exists in an encrypted vault namespace without revealing or returning its ciphertext

## Facts

- Endpoint: GET https://agentic-endpoints-testnet.oliver-835.workers.dev/vault/exists
- Price: $0.001/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/vault-key-existence-check-f7f29955
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_d3K0LTc29DVkZURFf3HNZ

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 vault-key-existence-check-f7f29955
```

Example prompt: Can you check whether the key 'api_credentials' exists in vault namespace 'myapp-prod' without retrieving its contents — I have the namespace token ready.

## When to prefer this

Use this endpoint when you need to confirm key presence in an encrypted vault namespace without the overhead or risk of retrieving and decrypting the value. Prefer this over the full retrieval endpoint when you only need a boolean existence check, want to avoid unnecessary data exposure, or are implementing pre-write deduplication logic or conditional branching in an agent workflow.

## Known failure modes

- Invalid or expired namespace_token returns an authorization error
- Key not found returns a false/absent status rather than an error
- Missing required parameters (key, namespace, or namespace_token) returns a validation error
- Namespace does not exist returns an error or not-found response
- Rate limiting or payment failure returns a 402 Payment Required or similar error

## How this service works

Check whether a key exists in the vault without returning its ciphertext (requires the namespace_token)

## Output

A boolean or status response indicating whether the specified key exists within the given vault namespace, without exposing any ciphertext or plaintext value associated with the key.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "key": {
   "type": "string",
   "description": "Item key to test"
  },
  "namespace": {
   "type": "string",
   "description": "Vault isolation scope"
  },
  "namespace_token": {
   "type": "string",
   "description": "One-time token issued when the namespace was claimed"
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/vault-key-existence-check-f7f29955/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from agentic-endpoints-testnet.oliver-835.workers.dev](https://www.zero.xyz/host/agentic-endpoints-testnet.oliver-835.workers.dev/llms.txt)