HMAC signature API: SHA-256 webhook signature check
Compute an HMAC of a message with a key using SHA-256 (default), SHA-1, SHA-384 or SHA-512, in hex and base64. Use to check webhook signatures. The key is used only for this call and is not stored.
When to use it
- Check webhook signatures
- Compute an HMAC with SHA-256 (default), SHA-1, SHA-384 or SHA-512 in hex and base64
$0.001 per call with prepaid credits: $1 by card pays for 1,000 calls, with no account and no subscription.
Inputs
| Name | Type | Description |
|---|---|---|
message (required) | string | The message |
key (required) | string | The key |
algorithm | string | sha256 (default), sha1, sha384 or sha512 |
Request
Over HTTP, with a card key from /credits:
curl -H "Authorization: Bearer adt_…" "https://glyphcall.com/hmac?message=hello&key=secret"Or one of your 3 free calls, no key:
curl "https://glyphcall.com/hmac?message=hello&key=secret&trial=1"Without a key, the same URL answers 402 Payment Required with x402 and MPP terms, so an agent with a wallet pays per call in USDC (Base, Polygon, Arbitrum or Solana over x402; Base or Tempo over MPP) and retries.
Example result
{
"algorithm": "sha256",
"hex": "88aab3ede8d3adf94d26ab90d3bafd4a2083070c3bcce9c014ee04a443847c0b"
}From an AI agent (MCP)
Add the MCP server to Claude, Cursor or any MCP client. This tool is hmac, and the first 25 successful calls are free:
https://glyphcall.com/mcpQuestions
Is my key stored?
No. The key is used only for this call and is not stored.
How do I pay?
Each successful call costs $0.002; failed calls are not charged. The first 3 calls are free (25 through an MCP client). Then pay with card credits (from $1; the key goes in an Authorization header or, for clients that can only fetch a URL, as api_key= in the URL) or per call in USDC over x402 or MPP. No account is needed.