HMAC Signing Skill

Overview

Returns the HMAC signature in hex or base64 encoding. Use for signing API requests, validating webhooks, or any scenario requiring message authentication.

Live Test HMAC Signing Skill Skill →

The tool

Once your client is connected to the VerveKit server, this appears in its tool list as HMACSigningSkill. It is read-only and open-world — it fetches and never mutates anything on your side — so most clients call it without asking you to confirm.

Tool call

{
  "name": "HMACSigningSkill",
  "arguments": {
    "message": "Hello World",
    "secret": "my-secret-key"
  }
}

You do not name the tool yourself; the model picks it. Asking about Hello World in the terms this skill covers is enough for it to reach for HMACSigningSkill on its own — naming it explicitly also works, and is the way to force the call.

Connecting

One server URL covers every skill in the catalog, including this one. Authorization is OAuth: the client opens a browser once, and there is no key to paste into a config file.

{
  "mcpServers": {
    "vervekit": {
      "url": "https://api.vervekit.com/v1/mcp"
    }
  }
}

Per-client setup — Claude, Cursor, VS Code, ChatGPT — is on the MCP setup page.

Arguments

These are the properties on the tool's inputSchema, so a well-behaved client validates them before the call is made. Premium arguments are accepted on every plan but only take effect on plans that include them.

Argument	Type	Description
`message`Required	string	The message to sign
`secret`Required	string	The secret key for HMAC generation
`algorithm`Optional	string	Hash algorithm to use `sha256sha384sha512sha1md5` default sha256
`encoding`Optional	string	Output encoding format `hexbase64` default hex

What the model gets back

The result carries a structuredContent object matching the tool's declared outputSchema, so a client reads fields without parsing prose. status is "ok" and error is null on success; a null field means the value was not available for that input, not that the call failed.

Result

{
  "status": "ok",
  "error": null,
  "data": {
    "hmac": "2cd7c25025198d4458002ceb064ad37ccfbbe46650876d693f5e080bd954e449",
    "algorithm": "sha256",
    "encoding": "hex"
  }
}

Response fields

Paths are relative to data. Premium fields are absent rather than zeroed on plans that do not include them, so check for presence instead of comparing to 0.

Field	Type	Example	Description
`hmac`	string	`2cd7c25025198d4458002ceb064ad37ccfbbe46650876d693f5e080bd954e449`	Generated HMAC signature in specified encoding format
`algorithm`	string	`sha256`	Hash algorithm used for HMAC generation
`encoding`	string	`hex`	Output encoding format applied to the signature

Failure modes

Errors come back as tool errors carrying a sentence the model can act on, not a bare status code. Error handling covers the full list.

Status	What it means
`400` / `422`	The arguments did not validate. The message names the offending one.
`401`	The OAuth session is invalid or expired — reconnect the server.
`403`	Blocked by a key restriction or an IP allow-list. Never a bad identity.
`404`	This skill is not part of VerveKit. Check the catalog.
`429`	Out of credits, or a brief rate limit. The message tells them apart.

A call costs 2 credits each time the tool actually runs; a model that reasons about the tool without calling it costs nothing.

Use cases

API Authentication: Sign API requests to prove authenticity
Webhook Verification: Validate incoming webhooks from services like Stripe, GitHub
Data Integrity: Ensure messages haven't been tampered with
JWT Signing: Generate signatures for JSON Web Tokens

Other ways to use HMAC Signing Skill

Set up HMAC Signing Skill on VerveKit, or reach the same source a different way. Your VerveKit account and credits work on all of them — one key, one balance.

Call it as a REST APIOne HTTPS endpoint and an x-api-key header, with SDKs for Node, Python and .NET.APIVerve →Reference →