sdxc APIs — pay-per-call package APIs

How charging works

Every priced call uses the x402 protocol. No API keys, no accounts — a wallet settles USDC on the configured network.

Call an operation or MCP tool without payment.
The server answers HTTP 402 with a PAYMENT-REQUIRED header (amount, network, destination).
Your client signs a payment and retries with PAYMENT-SIGNATURE.
We verify and settle through a facilitator, then return the result with PAYMENT-RESPONSE.

GET /, GET /v1, GET /health and MCP discovery stay free. Only running an operation charges.

Connect over MCP

Point your agent at the Streamable HTTP endpoint. Tool names match the catalog ids, so semver.satisfies is the same on HTTP and MCP.

Endpoint

https://api.sdxc.dev/mcp

Claude Code

claude mcp add --transport http sdxc-apis https://api.sdxc.dev/mcp

Cursor / clients with an MCP config file

{
  "mcpServers": {
    "sdxc-apis": {
      "type": "http",
      "url": "https://api.sdxc.dev/mcp"
    }
  }
}

Claude Desktop (HTTP bridge)

{
  "mcpServers": {
    "sdxc-apis": {
      "command": "npx",
      "args": [
        "-y",
        "@abluva/mcp-remote@latest",
        "https://api.sdxc.dev/mcp",
        "--protocol",
        "2026-07-28"
      ]
    }
  }
}

Unpaid tools/call requests answer HTTP 402 with the same x402 headers as POST /v1/…. Your MCP client needs an x402-aware wallet or bridge to settle.

Operations

Each row wraps one published package. Prices are USDC atomic units (6 decimals) on the configured network.

Id	Package	Price
`qr.encode` Encode text as a QR Code Model 2 symbol and return its SVG path.	@sdxc/qr	$0.001
`highlight` Tokenize source text for a named language with @sdxc/highlight.	@sdxc/highlight	$0.002
`markdown.plain` Parse Markdown and return plain text suitable for excerpts and search.	@sdxc/markdown	$0.001
`semver.satisfies` Ask whether one SemVer stands in a named relation to another (= != < <= > >= ~ ^).	@sdxc/semver	$0.0005
`zone-file.parse` Parse an RFC 1035 master file into typed DNS records (requires an origin).	@sdxc/zone-file	$0.002
`json-patch.apply` Apply an RFC 6902 JSON Patch document to a JSON value.	@sdxc/json-patch	$0.001
`json-patch.diff` Generate an RFC 6902 JSON Patch that transforms one JSON value into another.	@sdxc/json-patch	$0.001
`pdf.build` Build a one-page PDF from title, body text and a client-supplied TrueType font (base64, ≤ 500 KiB).	@sdxc/pdf	$0.005
`epub.build` Build an EPUB 3.3 publication from metadata and XHTML chapters; returns the container as base64.	@sdxc/epub	$0.005
`feed.normalize` Parse feed text or fetch a feed URL (≤ 1 MiB body, public hosts) into the normalized @sdxc/feed shape.	@sdxc/feed	$0.003

Call over plain HTTP

POST /v1/<id> with a JSON body. Same prices and payment headers as MCP.

# 1. Challenge
curl -i -X POST https://api.sdxc.dev/v1/semver.satisfies \
  -H 'content-type: application/json' \
  -d '{"version":"1.2.3","comparison":"^","against":"1.0.0"}'
# → 402 + PAYMENT-REQUIRED

# 2. Retry with PAYMENT-SIGNATURE from your x402 wallet
# → 200 + PAYMENT-RESPONSE + JSON result