# Where the Personal Agent Protocol fits among agent protocols

> PAP covers whether the customer has allowed this agent to act on their account, and how far. MCP moves tool calls, A2A lets agents talk, UCP and ACP handle shopping and payment, TAP proves an agent's identity, and PACT goes after the same consent problem as PAP.

Source page: https://pap.md/compare  
Last checked against sources: Oct 8, 2026  
pap.md is independent and not affiliated with Sierra, Meta or any PAP partner.

| Protocol | Backed by | Since | Covers | Overlap with PAP | Comparison |
| --- | --- | --- | --- | --- | --- |
| PAP (Personal Agent Protocol) | Sierra, Meta | Oct 6, 2026 | Agent sign-in, customer consent (read-only or write), route choice | n/a |  |
| MCP (Model Context Protocol) | Anthropic | Nov 2024 | Tools and data an AI app can call | low | https://pap.md/compare/pap-vs-mcp |
| A2A (Agent2Agent) | Google, now a Linux Foundation project | Apr 2025 | How two agents talk to each other | medium | https://pap.md/compare/pap-vs-a2a |
| UCP (Universal Commerce Protocol) | Google, with Shopify and retailers | Jan 11, 2026 | The shopping flow: discovery, checkout, after-sale | medium | https://pap.md/compare/pap-vs-ucp |
| ACP (Agentic Commerce Protocol) | OpenAI and Stripe | Sep 29, 2025 | In-agent checkout and payment tokens | medium | https://pap.md/compare/pap-vs-acp |
| TAP (Trusted Agent Protocol) | Visa and Cloudflare | Oct 14, 2025 | Proving an agent’s identity on each request | high | https://pap.md/compare/pap-vs-tap |
| PACT (Personal Agent Consent & Trust Protocol) | Decagon and Instinct | Oct 6, 2026 | Agent identity and customer authority, agent-to-agent | high | https://pap.md/compare/pap-vs-pact |

## Verdicts

- **PAP vs MCP:** Complementary. PAP decides whether the agent gets in and how far; MCP is one of the doors it can use.
- **PAP vs A2A:** Mostly complementary, with one overlap to watch: the "company agent" route.
- **PAP vs UCP:** Different layers with a shared border. Expect retailers to need both.
- **PAP vs ACP:** Complementary today. If PAP’s payment extension ships, Stripe will be the one deciding how much they overlap.
- **PAP vs TAP:** High overlap in purpose, low overlap in mechanism. A business may end up checking both.
- **PAP vs PACT:** Direct overlap. PACT is now an input to the PAP working group rather than a rival, at least on paper.

## Sources

1. [Introducing Personal Agent Protocol](https://sierra.ai/blog/introducing-personal-agent-protocol) · Sierra (Bret Taylor, Clay Bavor), Oct 6, 2026
2. [Model Context Protocol](https://modelcontextprotocol.io) · modelcontextprotocol.io
3. [Agent2Agent (A2A) Protocol](https://a2a-protocol.org) · a2a-protocol.org
4. [Under the Hood: Universal Commerce Protocol (UCP)](https://developers.googleblog.com/en/under-the-hood-universal-commerce-protocol-ucp/) · Google Developers Blog
5. [Stripe powers Instant Checkout in ChatGPT and releases Agentic Commerce Protocol codeveloped with OpenAI](https://stripe.com/newsroom/news/stripe-openai-instant-checkout) · Stripe, Sep 29, 2025
6. [Getting Started with Visa's Trusted Agent Protocol](https://developer.visa.com/capabilities/trusted-agent-protocol/docs-getting-started) · Visa Developer
7. [Introducing the Personal Agent Consent & Trust Protocol (PACT)](https://decagon.ai/blog/introducing-the-personal-agent-consent-trust-protocol-pact) · Decagon, Oct 6, 2026
8. [Meta's Personal Agent Protocol Signs Walmart Before It Has a Spec](https://www.beri.net/article/meta-sierra-personal-agent-protocol-oauth-guest-read-write-access-vs-ucp-acp-trusted-agent-protocol-retail-banks) · BERI