Cosign
Free a16z professional network for the startup world: endorsed talent profiles, curated lists, private Would Hire signals and startup jobs, with an API and MCP.
Free MCP server API
Bottom line
Cosign is a free a16z network of endorsed startup talent, curated lists and startup jobs. Recruiters hiring for startups get warm context on who is worth calling and a mutual-interest Would Hire signal, plus a free API and MCP server, but it covers the startup world only and has no recruiter seats or exports.
Stands out for: Profiles carry endorsements from named people saying what someone actually did, which is the context a reference call usually gives you. The Would Hire signal only opens a chat when interest is mutual, so outreach starts warm, and the official MCP server lets you search people and jobs from Claude or ChatGPT.
Watch out for: Coverage is limited to startups and tech, and the product is new. Many profiles are assembled by AI from public information before the person joins, so details can be wrong. There is no Boolean search, contact data, export or ATS sync, so it is a discovery and warm-intro tool rather than a sourcing database.
Overview
Cosign is a free professional network from a16z for the startup ecosystem. Members cosign people and companies they believe in and explain why, so profiles show attributed endorsements instead of only job titles.
Alongside the profiles sit curated and community lists, a jobs board pulled from company career pages, and an Industry Watch feed of company updates, talent moves and funding.
Private signals such as Would Hire and Would Meet let a member show interest without a public post, and a private conversation opens only when the interest is mutual.
AI researches and organises public information, so many profiles exist before the person joins. The person can claim, correct or remove a profile.
Cosign has a free public REST API for its people and company directories, with no key needed, and an OAuth member MCP server at api.cosign.co/mcp for Claude, ChatGPT and other MCP clients.
Who it's for
Best for
- Recruiters hiring for venture-backed startups
- Finding engineers and operators with peer endorsements
- Warm, mutual-interest outreach to passive talent
- Teams that want startup talent search inside Claude or ChatGPT
Not ideal for
- Volume hiring outside tech
- Teams that need emails, phone numbers or exports
- Agencies that need ATS or CRM sync
Key features
Endorsed profiles. People and company profiles carry attributed cosigns that say what someone contributed and why the endorser trusts them.
Curated and community lists. Members build public lists of breakout talent and companies, and community lists rank answers to questions like who to hire for a kind of work.
Private signals. Send Would Hire, Would Meet, Would Work With or Worked Together signals; a private conversation opens when interest is mutual.
Startup jobs. Open roles pulled from company job boards, with saved jobs and Apply links to the employer's own page.
Industry Watch. A feed of company updates, talent moves and funding news, plus public dashboards on AI labs and compute companies.
API and MCP. A free public REST API for the people and company directories, and an OAuth member MCP server at api.cosign.co/mcp.
AI features
| What the AI does | Plan |
|---|---|
| AI researches and organises public information into people and company profiles, talent moves and funding summaries | Free |
| Ask Cosign chat answers questions about people, companies and lists | Free |
Only features named in the vendor's own documentation. Anything sold separately is marked as an add-on.
MCP server
https://api.cosign.co/mcp
First-party MCP at api.cosign.co/mcp. Official a16z-hosted server over Streamable HTTP with OAuth 2.1 (PKCE) sign-in, free with a Cosign account. Members can find people, companies and jobs, read their own connection requests, and edit their profile, lists, requests and saved jobs; company scopes cover companies you manage. Request member:read for a read-only connection, since leaving scopes out grants read and write. Limits are 120 requests a minute per connection, and AI tools share 3 a minute, 20 an hour and 60 a day per account.
Setup steps and live status MCP Directory Check your stack in the MCP readiness checker
Pricing
Cosign is free. a16z runs it as a free product and lists no paid plans, seats or credits. The public directory API needs no key, and the member MCP server is free with a Cosign account. Confirm current terms on the vendor site.
Checked 2 Nov 2026. Vendors change prices without notice.
Is Cosign expensive?
Cosign starts at Free. We list 175 sourcing tools in total. 37 have a free tier, and those with a public price typically start around $99 a month.
- 59 quote-based
- 37 free tier
- 96 public price
Worked out automatically from every sourcing listing, so it updates as the directory changes.
Pros and cons
Pros
- Completely free, including the API and MCP
- Named, attributed endorsements on profiles
- Mutual-interest signals keep outreach warm
Cons
- Startup and tech coverage only
- AI-built profiles can be inaccurate
- No contact data, export or ATS sync
Integrations
Claude ChatGPT
What's new at Cosign
No updates logged yet. Follow Cosign and we will email you when it announces something new or its starting price changes.
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How Cosign compares
See all Cosign alternatives, with what each one does differently and a head to head for every pairing.
| Tool | Free tier | From | MCP | API | Compare |
|---|---|---|---|---|---|
| | ✓ | Free | ✓ | ✓ | |
| | ✓ | Free + paid seats | – | – | Compare |
| | – | $24/mo | – | – | Compare |
| | ✓ | Free | – | – | Compare |
Free + paid seats Free tier
Wellfound is the established startup jobs marketplace with paid recruiter seats, while Cosign is free and built around peer endorsements rather than candidate applications.
$24/mo
Happenstance searches your own network for warm intros from $24 a month, while Cosign is free and shows public endorsements across the whole startup community.
Free Free tier
Work at a Startup is Y Combinator's hiring platform for YC companies only, while Cosign is open to any startup and adds endorsed talent profiles.
Your next step
Shortlisting Cosign?
Still deciding? Ask an AI assistant about Cosign.
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