# 561 Group Market: Reading Knowledge Join

> 561 Group Market: Reading Knowledge Join is a paid API for AI agents from market.561.group, paid per call via x402, $0.001/call, status unknown (last checked 2026-10-31).

Joins reading and knowledge records via a machine-payable HTTP 402 endpoint, returning structured JSON results paid per-request in USDC on Base.

## Facts

- Endpoint: POST https://market.561.group/v1/four/reading-knowledge-join?utm_source=zero.xyz
- Price: $0.001/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-31
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/561-group-market-reading-knowledge-join-04f2ee6d
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_tK1swCDYFmDuBSiI-Bcpr

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 561-group-market-reading-knowledge-join-04f2ee6d -d '<json body>'
```

Example prompt: Look up the knowledge record joined with my reading entry and give me the combined structured result — I'll pay per request in USDC on Base via x402, no API key needed.

## When to prefer this

Choose this endpoint when you need a per-request, accountless, keyless lookup that joins reading and knowledge records, and you are able to pay $0.001 USDC per call on Base via the x402 protocol. Prefer this over traditional API-key services when building autonomous agents that need frictionless micropayment-based access without credential management.

## Known failure modes

- Payment failure: insufficient USDC balance on Base causes HTTP 402 rejection
- Invalid join parameters: malformed or missing input fields return an error
- No matching record: the reading or knowledge identifier does not exist, returning empty or null result
- Network timeout: Base network congestion delays payment confirmation
- Schema mismatch: response structure varies (contested schema) and may not match expected fields

## How this service works

Machine-payable x402 offers and books: software pays per request in USDC on Base over HTTP 402, with no account or API key.

## Output

A structured JSON object containing the joined reading and knowledge record data. The exact schema is labeled 'contested' indicating dynamic or variable output structure depending on the input parameters provided.

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": "contested"
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/561-group-market-reading-knowledge-join-04f2ee6d/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from market.561.group](https://www.zero.xyz/host/market.561.group/llms.txt)