yc-reader

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.

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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.

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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

Batch name format

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.

Industry and tag name format

Use lowercase with hyphens for multi-word names: real-estate, developer-tools, machine-learning.

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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

1. Use -s flag with curl to suppress progress output
2. Pipe through jq for readable output and filtering
3. Avoid fetching companies/all.json unless necessary — it's a large response (~5,700 companies). Prefer more specific endpoints (batches, industries, tags) when possible
4. Use jq select/filter to narrow results client-side when the API doesn't have a specific endpoint for what the user wants
5. Batch names are lowercase with hyphens — winter-2025 not Winter 2025 or W25
6. 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

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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.

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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'

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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.