If you are doing this for federated identity (single machine/human using multiple services) then use a purpose-built system for that.
Federated identity is hard to build correctly and unlikely to be important enough to your business to be a core competency that you'll justify maintaining properly.
I recommend using SAML 2.0 because it is broadly deployed and supported. Many implementations (including Shibboleth/OpenSAML) have been extensively pen-tested.
JWT is very similar to SAML, but is still evolving and the inconsistencies in implementations could make it frustrating to deploy successfully.
Both are based on sound cryptographic techniques and deploying them securely depends fundamentally on effective key management. Using a single private key for signing SAML Assertion or JWT Tokens for an excessive time period, volume of assertions/tokens, or after suspected compromise of a system with plaintext key access compromises the security of all federated services.