SEP submission: Tool Outcome Attestation extension (dev.agentstatus/toa)

Author: dulrajnrCreated Sep 6, 2026Updated Sep 12, 2026

Summary

Extensions Track SEP submission for Tool Outcome Attestation (TOA).

MCP defines how clients invoke tools. It does not define a shared, negotiable way to require attested delivery outcomes. Protocol success (JSON-RPC ok / HTTP 200) is not delivery success.

This issue tracks a ready SEP + reference implementation. A direct pull request into seps/ could not be opened: this repository currently limits PR creation to collaborators.

Extension

Id (incubating): dev.agentstatus/toa (SEP-2133 reverse-DNS for agentstatus.dev)
Type: Extensions Track
Primary protocol target: 2026-07-28 (server/discover + per-request clientCapabilities)
Evidence format: portable signed toa/0.1 (offline verify; no vendor account required to verify)

SEP text (ready to land under `seps/`)

Reference implementation

https://github.com/Carmel-Labs-Inc/toa

Includes schema + offline verify, wire binding validate/attach, MCP Python SDK ToaAttachExtension, conformance T1–T10, and E2E against official mcp 2.1+ (2026-07-28 advertise → attach → require → fail-closed, including stdio subprocess).

Relation to ATSA (SEP-2809)

Complementary, not competing:

	ATSA	TOA
When	Before dispatch	On / after tool result
Object	Server admission / identity	Tool call delivery outcome

Ask

A collaborator opens the SEP PR from dulrajnr:mcp-sep-toa:sep/tool-outcome-attestation into seps/ (or invites collaborator access so the author can).
Security IG tracks this next to ATSA without conflating admission and outcome.
Sponsor per SEP workflow when someone is willing to champion it.

Prior context

Docs-only optional verify in modelcontextprotocol/conformance#479 was closed with guidance to propose an extension with tests. This is that submission.

Source: modelcontextprotocol/modelcontextprotocol

View original on GitHub View discussion on GitHub