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Where the Personal Agent Protocol fits among agent protocols

PAP covers one question the others leave open: has the customer allowed this agent to act on their account here, and how far? MCP moves tool calls. A2A lets agents talk. UCP and ACP handle shopping and payment. TAP proves an agent's identity. PACT, launched the same day as PAP, goes after the same consent problem.

That's a lot of acronyms for one shopping trip, and we think some of them will merge or fade. For now, here's how they line up based on what each project has actually published.

ProtocolBacked bySinceCoversOverlap with PAP
PAPSierra, MetaOct 6, 2026Agent sign-in, customer consent (read-only or write), route choicen/a
MCP
Model Context Protocol		AnthropicNov 2024Tools and data an AI app can callLow
A2A
Agent2Agent		Google, now a Linux Foundation projectApr 2025How two agents talk to each otherSome
UCP
Universal Commerce Protocol		Google, with Shopify and retailersJan 11, 2026The shopping flow: discovery, checkout, after-saleSome
ACP
Agentic Commerce Protocol		OpenAI and StripeSep 29, 2025In-agent checkout and payment tokensSome
TAP
Trusted Agent Protocol		Visa and CloudflareOct 14, 2025Proving an agent’s identity on each requestHigh
PACT
Personal Agent Consent & Trust Protocol		Decagon and InstinctOct 6, 2026Agent identity and customer authority, agent-to-agentHigh

Read them as layers

Where PAP sits among agent protocols Four questions an agent visit has to answer, top to bottom. Identity, is this request really from that agent: TAP from Visa and Cloudflare, and Web Bot Auth. Consent, who sent it and what may it do: PAP from Sierra and Meta, and PACT from Decagon and Instinct. Transport, how requests travel: MCP and A2A. Commerce, how it shops and pays: UCP from Google and ACP from OpenAI and Stripe. This is pap.md’s reading of published scopes, not an official model. Where PAP sits among agent protocols pap.md’s reading of what each project has published. Not an official model. IDENTITY Is this request really from that agent? TAP Visa · Cloudflare Web Bot Auth IETF draft CONSENT Who sent it, and what may it do? PAP Sierra · Meta PACT Decagon · Instinct TRANSPORT How do the requests travel? MCP Tools and data A2A Agent to agent COMMERCE How does it shop and pay? UCP Google ACP OpenAI · Stripe PAP reflects the Oct 6, 2026 announcement; the v0.1 spec is pending. Each pairing, with sources: pap.md/compare.
Our read of published scopes, not an official model. PNG

Picture a customer's agent arriving at a store. TAP-style signatures can tell the store which agent this is. PAP tells it which customer sent the agent and whether it may change anything. MCP or A2A carry the actual requests. UCP or ACP take over at the cart and the card.

That's the tidy version. In practice the borders are fuzzy: PAP lists payments as a future extension, UCP has its own discovery, and PACT tackles consent too. The pages below go into each seam.

The comparisons

  • 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 · Sierra (Bret Taylor, Clay Bavor), Oct 6, 2026 · primary source
  2. Model Context Protocol · modelcontextprotocol.io · primary source
  3. Agent2Agent (A2A) Protocol · a2a-protocol.org · primary source
  4. Under the Hood: Universal Commerce Protocol (UCP) · Google Developers Blog · primary source
  5. Stripe powers Instant Checkout in ChatGPT and releases Agentic Commerce Protocol codeveloped with OpenAI · Stripe, Sep 29, 2025 · primary source
  6. Getting Started with Visa's Trusted Agent Protocol · Visa Developer · primary source
  7. Introducing the Personal Agent Consent & Trust Protocol (PACT) · Decagon, Oct 6, 2026 · primary source
  8. Meta's Personal Agent Protocol Signs Walmart Before It Has a Spec · BERI

pap.md is independent and not affiliated with Sierra, Meta or any PAP partner. Facts here come from the sources listed on each page.