Index Ventures has 317 portfolio companies tracked on the network, of which 315 — 99% — publish APIs indexed here.
Three hundred and seventeen companies at 99%. Sequoia, covered earlier this week, tracks 116 at 96%. Index’s book is nearly three times larger and its in-network rate is higher.
The top of the book
| Company | APIs | Composite | Agent readiness |
|---|---|---|---|
| Notion | 6 | 79.1 | 57.4 · agent-ready |
| Figma | 16 | 76.8 | 55.9 · agent-ready |
| Plaid | 31 | 75.2 | 53.4 · agent-native |
| Anthropic | 24 | 75.0 | 57.7 · agent-ready |
| Temporal | 7 | 73.0 | 41.4 · agent-ready |
| Adyen | 202 | 72.3 | 56.3 · agent-ready |
| Stack Overflow | 14 | 72.0 | 33.8 · agent-aware |
| Parallel | 6 | 69.2 | 61.0 · agent-ready |
| Stytch | 47 | 67.8 | 53.2 · agent-ready |
| Fireblocks | 35 | 67.2 | 41.0 · agent-ready |
| Mistral | 11 | 65.6 | 32.0 · agent-aware |
| evervault | 12 | 64.0 | 50.2 · agent-ready |
Eleven of twelve are exemplar. Plaid is the only agent-native entry, and it gets there on 31 APIs.
Two firms, two shapes
The overlap between these books is small and instructive. Notion, Figma, and Temporal appear in both. Everything else diverges.
Sequoia’s top twelve is anchored by the largest platform surfaces in software — GitHub’s 384 APIs, HubSpot’s 93, ServiceNow’s 63, Oracle’s 56. Index’s is anchored by narrow infrastructure primitives: Plaid, Stytch, Fireblocks, evervault, Parallel, Temporal. Six of the twelve do one technical job — bank data, auth, custody, encryption, retrieval, durable execution — and describe that job precisely.
The median API count in Index’s top twelve is around a dozen, against Sequoia’s several dozen. Different investment shape, visible entirely through published artifacts.
Small surfaces, high agent readiness
Parallel scores 61.0 on agent readiness with 6 APIs — the highest agent score in this table and one of the highest anywhere, from one of the smallest surfaces.
That keeps recurring. Zapier led Sequoia’s book on agent readiness with 13 APIs. Plaid reaches agent-native on 31. Meanwhile Adyen carries 202 APIs and scores 56.3, and Stack Overflow, at a 72.0 composite, sits at 33.8 — agent-aware.
The pattern is now consistent enough to state plainly: agent readiness is a property of precision, not breadth. A small surface with verified idempotency, described error semantics, a rate-limit signal in the contract, and unambiguous auth beats a large surface without them, every time. Adding endpoints does not move this number. Describing behaviour does.
Stack Overflow is the sharpest illustration. Excellent documentation, a genuinely exemplar composite, and the lowest agent readiness in the table — a surface built for humans reading a page, at the moment its most voracious consumers stopped being human.
Takeaway
317 portfolio companies, 315 with indexed APIs, and a top twelve built from narrow infrastructure primitives rather than broad platforms. Index’s book is a bet on companies that do one thing programmatically — and inside it, the six-API company scores higher on agent readiness than the 202-API one.
Browse the portfolio at apis.io/vcs/index-ventures/.