ATP MCP Server Specification
Track 3 Session 4 · April 2026 · Apache 2.0
Sections: Mandate Model · Tool Catalogue · NeMo & OAuth · Guest Agent & OCTO · Decisions
ACTIVITY TRAVEL PROTOCOL
1. Purpose and Scope
This document is the normative specification for the Activity Travel Protocol MCP Server — the primary AI agent integration surface for the Activity Travel Protocol runtime. It is the deliverable of Track 3 Session 4.
The ATP MCP Server exposes the Activity Travel Protocol Booking Object lifecycle to MCP-native AI agents. It implements the MCP specification version 2025-11-25 over Streamable HTTP transport (remote) and stdio (Tier 1 local). It is the package @atp/mcp-server in the Activity Travel Protocol SDK.
Decisions closed in this document: MCP-D1 through MCP-D12, OQ-SDK-2, OQ-SDK-3, OQ-AS-5, OQ-MCP-1.
1.1 Relationship to Protocol Architecture
MCP/A2A boundary (CLOSED): MCP governs Layer 3 (Workflow). A2A governs Layer 2 (inter-agent communication). The boundary is the Booking Object creation event. This is a foundational architectural decision and is not revisited.
The ATP MCP Server sits at the Layer 3 boundary. It translates MCP tool calls into Booking Object state machine events, enforced by the Security Kernel on every transition.
1.2 Three-Tier Deployment Posture
Tier Transport NeMo Auth Use Case Guardrails
Tier 1 stdio (local) Not applied OS-level Development, MyAuberge reference impl
Tier 2 Streamable HTTP Sidecar OAuth 2.1 / Production, container embedded AS single operator
Tier 3 Streamable HTTP NVIDIA AI Grid OAuth 2.1 / Hyperscale, stack enterprise IdP managed IaaS
2. Pre-Session Design Decisions
2.1 MCP Specification Version
The ATP MCP Server targets MCP specification version 2025-11-25 — the current stable release, now governed by the Agentic AI Foundation under the Linux Foundation. All normative references to MCP in this document are to this version.
2.2 MCP Tasks for HEM Invocation
Decision MCP-D3 (CLOSED): HEM invocations use MCP Tasks (experimental in spec 2025-11-25). The atp_invoke_hem tool is the sole async tool in the catalogue. This path is flagged EXPERIMENTAL, tracking MCP Tasks promotion to stable. The Activity Travel Protocol Foundation will re-evaluate at the next MCP spec revision.
2.3 Mandate Model Approach
Decision (Option C, CLOSED): The ATP Mandate model is specified normatively in this document. OVID (@clawdreyhepburn/ovid) is cited as the reference implementation and design source. The SDK dependency decision (adopt OVID directly vs. independent implementation in @activity-travel-protocol/security) is deferred to Track 3 Sessions 5/6.