# the402.ai Thread Message Sender

> the402.ai Thread Message Sender is a paid API for AI agents from api.the402.ai, paid per call via x402, $0.001/call, status down (last checked 2026-09-15).

Posts a new message to a specific thread on the the402.ai platform using an API key for free access

## Facts

- Endpoint: POST https://api.the402.ai/v1/threads/thread_f4a7d2a2575b4beb/messages
- Price: $0.001/call
- Payment: x402
- Status: down
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/api-the402-ai-aa99fe88
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_JGxBh6iPDwfMJayVeBVFY

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 api-the402-ai-aa99fe88 -d '<json body>'
```

Example prompt: Send the message 'Hello, can you summarize the latest project updates?' to thread thread_f4a7d2a2575b4beb on the402.ai.

## When to prefer this

Use this endpoint when you need to programmatically post messages into a specific the402.ai thread, particularly when operating with an API key for free-tier access. Prefer this over paid alternatives when your use case fits the free-with-API-key tier and you already have a valid thread ID on the platform.

## Known failure modes

- Invalid or missing API key returns 401 unauthorized
- Non-existent thread ID returns 404 not found
- Empty or malformed message body returns 400 bad request
- Rate limit exceeded returns 429 too many requests
- Payment or quota issues may return 402 payment required despite free tier claim

## How this service works

Send thread message (free with API key)

## Output

Returns confirmation of the message being posted to the thread, typically including a message ID, the thread ID, content echoed back, and a timestamp indicating when the message was created.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "required": [
  "id"
 ],
 "properties": {
  "id": {
   "type": "string"
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/api-the402-ai-aa99fe88/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.the402.ai](https://www.zero.xyz/host/api.the402.ai/llms.txt)