26/1166 → 55/1126; +2.65 percentage points of formation share.
Agents that buy services or transact with other agents may require accountable identity, delegated budgets, dispute handling, and machine-speed payment controls.
Look for production agent-to-agent transactions and document who bears liability, sets limits, verifies counterparties, and resolves failed work.
Application behavior increasingly depends on data, APIs, labels, prompts, and models whose changes are not represented in a single operational dependency graph.
Map production incidents to upstream data, API, labeling, and model changes, then test whether teams can predict affected behavior before release.
Companies like Kable (API billing) and Wingback (SaaS/API monetization) are already forming around the pain of metering and pricing API consumption, while API-first startups like SnapTrade, Vessel, and Pelm all need to charge downstream customers per-call or per-usage; this creates demand for a shared metering/billing layer that these niche players may standardize into.
Check back around June 2027 for new YC batches, to see whether independent evidence for "Unified API usage-based billing/metering infrastructure" has appeared.
Requestly (API testing/debugging) and Hyperbeam (embeddable API-based virtual environments) both point to increasing complexity in API integration testing, especially as Andi (generative AI search) and other AI-API hybrids proliferate, suggesting demand for specialized debugging tools tailored to AI-driven API calls.
Check back around April 2027 for new YC batches, to see whether independent evidence for "Developer-tooling for API testing/debugging in AI-integrated products" has appeared.
Pelm (energy data APIs) and Emobi (EV/energy APIs) both aggregate fragmented data sources in the energy vertical, similar to how SnapTrade aggregates brokerage APIs in fintech; this pattern suggests other fragmented verticals (health, identity) will spawn their own normalization APIs, as seen with Serif Health and Prembly already tackling healthcare and identity respectively.
Check back around May 2027 for new YC batches, to see whether independent evidence for "Vertical-specific API aggregation/normalization layers" has appeared.
Sohar Health is an AI-driven front-end RCM solution that transforms insurance verification processes for healthcare providers, enabling faster patient conversions and reducing administrative workloads. With a 95% automation rate, our API-first platform seamlessly integrates into existing workflows to provide real-time claim accuracy and eligibility checks. Key performance metrics showcase the power of our technology: Median latency of just 6 seconds, ensuring real-time eligibility; over 90% of checks returned within 30 seconds for increased patient conversion; 96% accuracy in identifying and verifying benefits details; Industry-leading 99% accuracy for eligibility determination; >90% carve-out detection rate, mitigating surprise billing risks; a 60% success rate with our Insurance Discovery API, helping identify coverage for self-pay patients. Our customers include outpatient clini
Terminal builds telematics data infrastructure for the commercial fleet industry. Commercial auto insurers and fleet software companies, including industry leaders like Intact Insurance, depend on our platform to access GPS, speeding, and vehicle data from 330+ telematics providers. We recently raised our Series A led by Battery Ventures and are backed by Y Combinator, Golden Ventures, Penske Transportation Solutions, and Intact Private Capital. Our team works together in person in Toronto, combining early-stage speed with late-stage maturity while processing many terabytes of vehicle data every day.
Skyvern helps companies automate browser based workflows using LLMs and Computer Vision, fully automating manual workflows and replacing brittle or unreliable scripts. Examples include: 1. Automating materials procurement from commerce websites 2. Completing complex multi-step workflows (ie getting an insurance quote from Geico.com) 3. Automatically logging into portals and downloading invoices 4. Navigating legacy content systems to do data extraction or data entry
The first version of RecipeUI was a viral project at Robinhood that reached 100% adoption from all engineering and QA teams. When an API broke, anyone from Frontend to QA to PMs could debug without relying on backend engineers
Smobi is the AI-powered platform for branded, interactive business messaging, starting with RCS. We help businesses send rich, personalized messages that drive engagement, build trust, and create real conversations.
Generate AI agents with plain English, edit visually, customize with code in your own IDE. Currently automating millions of tasks across support, sales, finance and more for companies like eToro, Payoneer and JustEat.
Inconvo is the open-source platform for building data agents on production data. With safe queries, permissions, and structured outputs. Use Inconvo to build and deploy data agents that query production databases and can be called directly from your application. You get safe query execution, permissions, stateful conversations, and observability out of the box.
Specialized inference, built for agent workloads Fast Open-Source models: Kimi k3, Deepseek v4 flash, qwen 397b, at 200+ tps Specialized models for applying edits, code search, compaction, and model routing
Glide lets apps accept crypto deposits from any chain, wallet, or exchange using pre-built wallet funding flows. Users can fund wallets directly — no bridges, no swaps, no repeated KYC.
Opensteer creates specialized AI agents in cloud computers that can integrate with anything. Each agent gets customizable browser access, tools, instructions, and guardrails, so it can work 24/7 exactly the way you need.
A primary internal company segment within API, derived deterministically from the shared yc tag “Developer Tools”. This is a classification of current window members, not a causal layer or a separate time trend.
Measured-window members of API that could not be assigned to a narrower shared YC tag or industry without forcing a classification.
A primary internal company segment within API, derived deterministically from the shared yc industry “Engineering, Product and Design”. This is a classification of current window members, not a causal layer or a separate time trend.
A primary internal company segment within API, derived deterministically from the shared yc tag “Infrastructure”. This is a classification of current window members, not a causal layer or a separate time trend.
A primary internal company segment within API, derived deterministically from the shared yc tag “Payments”. This is a classification of current window members, not a causal layer or a separate time trend.
A primary internal company segment within API, derived deterministically from the shared yc tag “Digital Health”. This is a classification of current window members, not a causal layer or a separate time trend.
No comparable outside activity is connected yet.
These share a word with “API” but are tracked as separate categories. The real overlap below is the actual share of API’s companies also found in that category — not a guess.
Cambrian Signal, “API,” publication yc-2026-10-22-semantic-v8, snapshot October 22, 2026.
cambrian.jafar.com/formation/api