Zero. Out of 222 YC companies from the last four batches, not a single one has shipped an MCP server. The average agent-readiness score across Y Combinator's most recent cohorts is 32 out of 100.

These are supposedly the most technically ambitious startups in the world. Here's who's actually building for agents — and who isn't.

Mastra — 77/100 Open-source agent framework from YC W25. No auth required, free to use, and the only YC company to score above 75. Discovery and tooling both above 80. The catch: no MCP server and no OpenAPI spec. An agent can use it, but has to figure out the integration from docs. Still — this is what agent-readiness looks like when it's intentional.

Browser Use — 73/100 Also W25, also open-source. Lets agents control web browsers programmatically. Same pattern as Mastra: high scores because there's no auth wall and the API is clean. Same gap: no machine-readable interface description.

Bolna — 68/100 F25 batch. Voice agent framework with an actual OpenAPI spec — one of only 20 YC companies that published one. API key auth, free tier, sandbox available. This is the closest any YC company came to checking every box.

The pattern across all 222 scores: the companies building for agents (frameworks, dev tools) score well. The companies building with AI but serving humans through dashboards score poorly. 113 of 222 use OAuth2 as their primary auth — which means an agent needs a browser and a human to log in. Only 20 published an OpenAPI spec. Only 14 scored above 50.

The full ranked leaderboard — all 222 companies with scores, categories, and breakdowns — is live at agentnativeregistry.com/yc-leaderboard