JWT Toolkit – Sign

x402

JWT Toolkit – Sign is a paid API for AI agents from jwt.openverbs.com, paid per call via x402, $0.004/call, status unknown (last checked 2026-10-28).

Signs a JSON payload as a JWT using a specified algorithm and key, returning a signed token with configurable claims.

Price / call$0.004

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StatusUnknown

How this service works

Mint a signed JSON Web Token from a JSON claims object, using a shared secret (HS*) or a PEM private key (RS/ES/PS). Supports expiresInSec, notBeforeSec, issuer, audience, subject and keyid. An unusable key or option is rejected before payment.

Output

The endpoint returns a signed JWT string (compact serialization: header.payload.signature) that encodes the provided claims, ready to be used as a Bearer token or passed to any JWT-aware service for verification.

Example use cases

Issuing short-lived API access tokens

“Create a signed JWT using RS256 with my PEM private key, set the issuer to 'auth.myservice.io', subject to 'client-789', and make it expire in 900 seconds — don't include the timestamp.”

Generating user session tokens

“Sign a JWT with HS512 using the shared secret 'ultrasecretpassphrase', include the claims {userId: 'usr_001', role: 'admin'}, set the audience to 'dashboard.app', and have it expire in 86400 seconds.”

Minting tokens for microservice-to-microservice auth

“I need a JWT signed with ES256 using my PEM-encoded EC private key, with issuer 'service-orders', subject 'service-payments', kid set to 'key-v3', and expiry in 300 seconds.”

Technical details

Endpoint

POSThttps://jwt.openverbs.com/v1/sign?utm_source=zero.xyz

When to prefer

Choose this endpoint when you need to programmatically sign JWTs server-side without managing a local crypto library, or when running in an agent/serverless context where importing jsonwebtoken or similar is inconvenient. It supports the full suite of HMAC, RSA, ECDSA, and RSASSA-PSS algorithms. Prefer this over a full auth server when you only need token minting, not a complete identity management solution.

Side effects

Invalid or mismatched key for the chosen algorithm (e.g. passing an HMAC secret for RS256) returns a signing error
Malformed PEM-encoded key returns a key parsing error
Missing required fields (payload, key, algorithm) returns a validation error
Unsupported algorithm value returns an enum validation error
Key too short for the selected algorithm may return a security constraint error
Payment not attached or insufficient USDC balance returns a 402 Payment Required

Input

Schema · Request body

Field	Type	Description
key	string	The HMAC shared secret (HS*) or the PEM-encoded private key (RS/ES/PS).
keyid	string	Set the `kid` header.
issuer	string	Set the `iss` claim.
payload	object	The claims to encode (an object).
subject	string	Set the `sub` claim.
audience	string	Set the `aud` claim.
algorithm	string	Signing algorithm, one of HS256, HS384, HS512, RS256, RS384, RS512, ES256, ES384, ES512, PS256, PS384, PS512.
noTimestamp	boolean	Omit the automatic `iat` claim.
expiresInSec	integer	Set `exp` this many seconds from now.
notBeforeSec	integer	Set `nbf` this many seconds from now.

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