# MCP vs A2A: what products publish for AI agents

173 of the 200 products we checked have an MCP server. 24 publish an A2A agent card.

Drives: 1 Oct 2026 to 1 Nov 2026 · 200 products · Step: [Find](https://agentdrives.com/access/find.md) · Subject: Agent discovery files · Counted 1 Nov 2026. Source: https://agentdrives.com/findings/mcp-vs-a2a?via=md · CC BY 4.0

## What we found

| Of 200 products | Products | Share |
|---|---|---|
| An MCP server | 173 of 200 | 87% |
| An MCP server card | 49 of 200 | 25% |
| An A2A agent card | 24 of 200 | 12% |

| Of 148 sites | Sites | Share |
|---|---|---|
| llms.txt | 111 of 148 | 75% |
| auth.md | 17 of 148 | 11% |
| SKILL.md or an Agent Skills index | 9 of 148 | 6% |

- For every product with an A2A agent card, about 7 have an MCP server.
- 49 of the 200 publish an MCP server card, a file that describes the server at a fixed address.
- Of the 148 sites whose files we read, 111 publish an llms.txt, 17 an auth.md and 9 a SKILL.md or an Agent Skills index.

## For product owners

- Publish a server card next to your MCP server, so an agent can find the server without reading your docs first.
- Publish an A2A agent card at /.well-known/agent-card.json only if your product runs an agent other agents can call.
- Add an auth.md at the root of your site if an agent can sign up on its own. Say how it gets an account and a key.

## For agent builders

- Look for an MCP server first: 173 of 200 products have one.
- Don't count on an A2A agent card. 24 of 200 products publish one.
- Fetch /llms.txt and /auth.md before you sign up.

## How we tested

- Drives from 1 Oct 2026 to 1 Nov 2026, 201 products.
- At 200 of them, the drive asked the product's site for an MCP server card (at the MCP endpoint's /server-card, /.well-known/mcp/server-card.json and the AI Catalog at /.well-known/ai-catalog.json) and an A2A agent card (/.well-known/agent-card.json and the older /.well-known/agent.json). Only JSON with a JSON content type counts.
- At 148, we asked the site for /llms.txt (also on its docs. subdomain), /auth.md, /SKILL.md and /.well-known/skills/index.json.
- An MCP server counts when the drive found an official or third-party one, never one that only searches the docs.

## Limits

- Each site as it was on the day of its newest drive.
- A file at another address is not counted.
- We count that a file is there, not how good it is.
- A file fewer than 5 products publish is left out.

## Sources

- [Every number on this page, with its definition](https://agentdrives.com/data/facts.md?via=md#discovery.checked)
- [Agent access: Find](https://agentdrives.com/access/find.md)
- [What software sites publish for agents, in the monthly report](https://agentdrives.com/research/state-of-agent-access.md?via=md#adoption)
- [The MCP standard](https://agentdrives.com/standards/mcp.md)
- [How we drive](https://agentdrives.com/method.md?via=md)