Y Combinator Reader (Read-Only)
Fetches Y Combinator company data from the yc-oss/api, an unofficial open-source API that indexes all publicly launched YC companies. The data is sourced from YC's Algolia search index and updated daily via GitHub Actions.
This is a read-only data source. It provides company profiles, batch listings, industry/tag breakdowns, hiring status, and diversity data. No write operations exist — the API serves static JSON files.
No authentication required. The API is public and free. Just use curl to fetch JSON endpoints.
Step 1: Verify Prerequisites
This skill only needs curl (to fetch data) and jq (to parse/filter JSON). Both are pre-installed on most systems.
!`(command -v curl > /dev/null && echo "CURL_OK" || echo "CURL_MISSING") && (command -v jq > /dev/null && echo "JQ_OK" || echo "JQ_MISSING")`
If JQ_MISSING, install it:
# macOS
brew install jq
# Linux (Debian/Ubuntu)
sudo apt-get install jq
If jq is unavailable, you can still fetch raw JSON with curl and parse it inline with Python or other tools — but jq makes filtering much easier.
Step 2: Identify What the User Needs
Match the user's request to the appropriate endpoint. See references/api_reference.md for full details.
| User Request | Endpoint | Notes |
|---|
| Overall YC stats | meta.json | Company count, batch list, industry/tag lists |
| All companies | companies/all.json | Full dataset (~5,700 companies) — large response |
| Top companies | companies/top.json | ~91 top-performing YC companies |
| Companies hiring | companies/hiring.json | ~1,400 currently hiring |
| Non-profit companies | companies/nonprofit.json | YC-backed non-profits |
| Diversity data | companies/black-founded.json, hispanic-latino-founded.json, women-founded.json | Founder diversity |
| Specific batch | batches/{batch-name}.json | e.g., winter-2026.json, spring-2026.json, fall-2025.json |
| Single company profile | batches/{batch-name}/{slug}.json | e.g., batches/summer-2009/stripe.json, batches/winter-2009/airbnb.json |
| By industry | industries/{industry}.json | e.g., fintech.json, healthcare.json |
| By tag | tags/{tag}.json | e.g., ai.json, developer-tools.json |
Batches use {season}-{year} format: winter-2026, spring-2026, summer-2026, fall-2025. Older batches follow the same pattern back to summer-2005. The short form (w09, s21) also works for the per-company endpoint.
Use lowercase with hyphens for multi-word names: real-estate, developer-tools, machine-learning.
Step 3: Execute the Request
Base URL
https://yc-oss.github.io/api/
General pattern
# Fetch and pretty-print
curl -s https://yc-oss.github.io/api/companies/top.json | jq .
# Count companies in a result
curl -s https://yc-oss.github.io/api/batches/winter-2025.json | jq length
# Filter by field (e.g., hiring companies in a batch)
curl -s https://yc-oss.github.io/api/batches/winter-2025.json | jq '[.[] | select(.isHiring == true)]'
# Extract specific fields
curl -s https://yc-oss.github.io/api/companies/top.json | jq '.[] | {name, one_liner, batch, team_size, website}'
# Search by name (case-insensitive)
curl -s https://yc-oss.github.io/api/companies/all.json | jq '[.[] | select(.name | test("stripe"; "i"))]'
Key rules
- Use
-s flag with curl to suppress progress output
- Pipe through
jq for readable output and filtering
- Avoid fetching
companies/all.json unless necessary — it's a large response (~5,700 companies). Prefer more specific endpoints (batches, industries, tags) when possible
- Use
jq select/filter to narrow results client-side when the API doesn't have a specific endpoint for what the user wants
- Batch names are lowercase with hyphens —
winter-2025 not Winter 2025 or W25
- Tag and industry names are lowercase with hyphens —
developer-tools not Developer Tools
Common jq filters
| Filter | Purpose |
|---|
jq length | Count results |
jq '.[0]' | First company |
jq '.[:10]' | First 10 companies |
jq '[.[] | select(.isHiring == true)]' | Only hiring companies |
jq '[.[] | select(.status == "Active")]' | Only active companies |
jq '[.[] | select(.team_size > 100)]' | Companies with 100+ employees |
jq '.[] | {name, one_liner, batch, website}' | Select specific fields |
jq '[.[] | select(.name | test("query"; "i"))]' | Search by name |
jq 'sort_by(-.team_size) | .[:10]' | Top 10 by team size |
Step 4: Present the Results
Summarize rather than dump JSON. For each company, give the name, one-liner, batch, team size, status, hiring status (a growth signal), and website. For a batch, lead with its size and notable companies; for an industry or tag, the count and which companies are top or hiring; for research questions, aggregate stats such as counts, common industries, and team-size distribution. Mention that the dataset refreshes daily.
Step 5: Diagnostics
If a request fails:
| Error | Cause | Fix |
|---|
404 Not Found | Invalid batch, industry, or tag name | Check meta.json for valid names |
Empty array [] | No companies match the query | Broaden the search or check spelling |
curl: Could not resolve host | No internet connection | Check network connectivity |
| Large/slow response | Fetching companies/all.json (5,700+ entries) | Use a more specific endpoint or add jq filters |
To discover valid batch, industry, and tag names:
# List all batches
curl -s https://yc-oss.github.io/api/meta.json | jq '.batches[].name'
# List all industries
curl -s https://yc-oss.github.io/api/meta.json | jq '.industries[].name'
# List all tags (there are 333+)
curl -s https://yc-oss.github.io/api/meta.json | jq '.tags[].name'
Reference Files
references/api_reference.md — Complete endpoint reference with company schema, all endpoint URLs, and research workflow examples
Read the reference file when you need the exact company field schema, valid batch/industry/tag names, or detailed research workflow patterns.
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