The Index Ventures API Portfolio

About this paper

I read Index Ventures’s portfolio the way a machine reads it — not the pitch, the evidence. Index’s public portfolio resolves to hundreds of companies in my catalog, and 98 of them ship a public API I could pull, parse, and score on the same rubric I apply to Stripe. This report is about those 98, because the interface is the part of a company an integrator, an acquirer, or an agent can actually inspect — and a fund’s book of APIs is a truer signal of its bet than any thesis page.

The headline is a distinct one. Index does not run the widest API book — 98 scored providers, less than half of a16z’s 242 — but it runs one of the densest: six companies clear the exemplar band on a book of 98, an exemplar rate at the very top of every fund I have deeply harvested, and the estate skews late-stage and deep, with Adyen shipping 216 one-per-resource specs, Remote 101, Stytch 47, and Plaid a 265-operation monolith. It is a concentrated, enterprise-SaaS-pedigreed book with real agent depth at the top — Parallel and Remote ship both a hosted MCP server and authored agent skills, the double-threat most funds’ books lack. Yet the same 98 average a composite Kin Score of 50.8 — a dead heat with Lightspeed, a16z, and Accel — because at the mean every big fund’s API book looks the same. The differentiation lives at the top of the book and in agent depth, and this report reads that signal company by company: the practice-area decomposition, the Kin Score facet-by-facet, the twelve-dimension agent-readiness table, the head-to-head against eleven rival funds, and the punch-list of what even the crown jewels — governance, scope catalogs, idempotency, examples — have not shipped.

What's inside

1. Executive summary — the dense, deep book with a diligence-grade gap
2. The firm, and the book — the 98 API-bearing companies
3. Portfolio decomposition — enterprise-SaaS with an AI engine
4. The composite Kin Score of the book — and why governance is the weakness
5. Agent-readiness of the portfolio — depth over rate
6. The peer-fund benchmark — the dense book among the broad ones
7. The crown jewels — provider-by-provider on the six exemplars and top strong-band names
8. Standards and the agentic turn — why the gaps stop being pedantry
9. Security, auth, scopes, and compliance posture across the book
10. The AI question, and the whitespace for the fund and its rivals
11. The investable thesis — for Index, and for everyone reading it

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