# Capability Token

> A credential that encodes exactly what an agent may do, often including allowed tools, targets, budgets, expiry, and delegation limits.

- Category: Tools & Protocols
- Stage: Emerging
- Also called: Agent capability token, Invocation-bound token, Task-scoped warrant
- Canonical: https://www.joelcsaji.com/ai-dictionary/capability-token

## Plain English

It is a narrow permission slip for one agent task instead of a broad API key.

## Example

A refund agent receives a token that allows `refund.write` up to $50 for one customer and expires after the workflow ends.

## Why it matters

Capability tokens reduce ambient authority and give teams evidence for who authorized each tool-mediated action.

## Related

- [Agent Identity](https://www.joelcsaji.com/ai-dictionary/agent-identity)
- [Action-Time Authorization](https://www.joelcsaji.com/ai-dictionary/action-time-authorization)
- [Ambient Authority](https://www.joelcsaji.com/ai-dictionary/ambient-authority)

## Sources

- [arXiv: Agent Identity Protocol](https://arxiv.org/abs/2603.24775)
- [Tenuo: Task-Scoped Warrants](https://tenuo.ai)
- [Capframe: Capability Security](https://capframe.ai/)