Text embeddings

Generate a text embedding vector using OpenAI text-embedding-3-small (1536 dimensions). Send POST /api/embed with the required field text and pay $0.002 per call over x402 or MPP (there is no free tier). It returns a JSON object with model, provider, embedding, dimensions and usage.

Ideal for semantic search, RAG, and clustering. No API key needed; pay per call via x402. Text capped at 32k chars.

Category: AI & compute · Tags: embeddings vector rag semantic-search openai text-embedding-3-small

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Parameters

Example request

curl -i -X POST https://agent402.tools/api/embed \
  -H "Content-Type: application/json" \
  -d '{"text":"Agent402 is an open-source x402 tool server."}'

Without payment this returns HTTP 402 Payment Required with the exact price for embed; any x402 v2 or MPP client pays it and retries.

Example response

{
  "model": "text-embedding-3-small",
  "provider": "openai",
  "embedding": [
    0.0023,
    -0.0091,
    0.0152
  ],
  "dimensions": 1536,
  "usage": {
    "total_tokens": 12
  }
}

From an MCP client

catalog.call {
  "slug": "embed",
  "params": {
    "text": "Agent402 is an open-source x402 tool server."
  }
}

The hosted connector at https://agent402.tools/mcp needs a payment for embed; the stdio package pays it from a wallet or from AGENT402_CREDITS_KEY. Local install: npx -y agent402-mcp.

Errors and behavior

• text is required. An input the tool rejects returns an HTTP 4xx whose body carries error, tool, expected, required and example, so the caller can correct it.
• A paid call that ends in any status of 400 or above is not charged over x402, MPP or a prepaid credits key: settlement is cancelled when the tool fails. The exception is a Tempo push credential, a transfer the buyer sent before the call: it settles before the tool runs, so if the tool then fails the payment is recorded as a refund owed to the paying wallet.
• Wallet-only: this tool runs a model, so it has no proof-of-work tier. A prepaid card-credits key issued earlier (Authorization: Bearer a402_...) also pays it.
• Model-backed: the answer is generated by a model, so the same input can produce different wording.
• A GET or HEAD to /api/embed returns the same 402 quote, so the price can be read without a body.
• An Idempotency-Key header makes a retried paid call replay the first 200 instead of charging again (an answer larger than 1 MB is not replayed).

Paid call (JavaScript agent)

import { wrapFetchWithPayment } from "@x402/fetch";
import { x402Client } from "@x402/core/client";
import { registerExactEvmScheme } from "@x402/evm/exact/client";
import { privateKeyToAccount } from "viem/accounts";

const client = new x402Client();
client.setSpendControls?.(false); // keep your own spending ceiling in code
registerExactEvmScheme(client, { signer: privateKeyToAccount(KEY) });
const payFetch = wrapFetchWithPayment(fetch, client);

const res = await payFetch("https://agent402.tools/api/embed", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({
    "text": "Agent402 is an open-source x402 tool server."
  }),
});

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