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Verifiable receipts for AI agent spending

paymaster is a reference implementation for tracking who authorized an AI action, what policy decided, what it cost, and what the provider confirms. It is built for developers who need auditable evidence around autonomous spending, not a full financial control system.

Agenticness = how independently a tool can take action, scored across 9 dimensions. Scored independently by David Kooi, Skylark Creations — see full rubric → Last re-evaluated 29 August 2026.

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Open Source
API
B2B
For Developers
CLI
MCP Support
Self-Hosted
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About

What It Is

paymaster is an open-source reference implementation for verifiable AI agent-spend receipts. It focuses on the evidence chain around autonomous software: who acted, under whose authority, what policy decision was made, what was spent, and what the...

What to Know

This is not a production financial-control product. The author explicitly says it does not move money, hold keys, execute payments, or block actions; the gate runs in shadow mode, and agents with direct provider credentials can bypass it. Its main...

Key Features
Generates verifiable agent-spend receipts
Records authenticated principal and policy-hashed decisions
Reconciles known transactions against provider records
Flags coverage gaps and unknown outcomes
Exposes a CLI for ingesting, checking, reporting, and explaining receipts
Use Cases
Auditing AI agent actions after a provider bill arrives
Building an internal evidence trail for autonomous API spending
Inspecting whether a governed route reconciles to provider records
Agenticness: Guided Assistant

Executes tasks you assign, one step at a time, within narrow domains.

High evidence
Last evaluated: Aug 29, 2026

Dimension Breakdown

Action Capability
Autonomy
Planning
Adaptation
State & Memory
Reliability
Interoperability
Safety
Operator Sovereignty

Categories

Pricing
  • Free / open source — full functionality available at no cost.
Details
AddedAugust 29, 2026
RefreshedAugust 29, 2026
Agenticness
Quick Facts
DeploymentSelf-hosted
AutonomyCopilot (human-in-loop)
Model supportSingle model
Open sourceYes
MCP supportYes
Team supportIndividual only
Pricing modelFree / open source
Interfacecli, api
Sources
Last updated August 30, 2026
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