Callbook AI

AI collections agency for late stage portfolios

3.1Score#337 of 999 agents#10 of 27 in Billing and collections agent

Why it ranks #337

Callbook AI, an AI billing and collections agent from YC S26, ranks #337 of 999 AI agents and #10 of 27 in Billing and collections agent, with a score of 3.1 of 10. Data as of 3 Oct 2026.

The score adds four parts, each 0 to 10, by weight. Every point comes from public evidence. How scoring works ·

Proof 0 × 30% 0.0
Scale 3 × 30% 0.9
Momentum 4 × 25% 1.0
Autonomy 8 × 15% 1.2
= 3.1

Proof
Do customers use it? 30% of the score
0
No public claims of customers or revenue yet.
Not found: revenue or growth (+4), named customers (+3), a customer result (+2), a customer count (+2), work done at scale (+2)
Scale
Is there a real company behind it? 30% of the score
3
7 people.
- +3
  7 people on its YC page5 to 9 people
Not found: funding round in its news (+3)
Momentum
Is it shipping and growing now? 25% of the score
4
Shows a recent launch and a new batch.
- +3
  Launched in the last 6 monthsCallbook AI: The AI collections agency for late stage portfoliosLaunch YC post · 19 Aug 2026
- +1
  New: YC Summer 2026
Not found: open roles on YC (+2), new traction claim in the last 6 months (+2), funding news in the last year (+2)
Autonomy
How much of the job does it do on its own? 15% of the score
8
Autonomous worker: completes whole tasks; people handle exceptions.
- +8
  Level 3 of 4: Autonomous workerCompletes whole tasks; people handle exceptions.
What the model read
- Acts in other systems: 93% likely
- Finishes whole tasks: 62% likely
- Calls itself an agent: 6% likely
- An AI-native service: it sells the finished work, so it counts as an agent at any level
Level 3: Completes whole tasks; people handle exceptions.