jwt_decoder

JWT / Base64 Token Decoder Tool

An MCP-compatible agent tool that decodes and inspects JSON Web Tokens (JWT) headers and payload claims without verifying cryptographic signatures.

Parameters

• token (string, required): The raw JWT token string (header.payload.signature).

Output

Returns JSON containing:

• header: Parsed JWT header (e.g. algorithm, token type).
• payload: Decoded claims dictionary (e.g. sub, iss, aud, exp).
• is_expired: Boolean indicating if the exp timestamp has passed.
• expires_in_seconds: Remaining lifespan in seconds (or negative if expired).