MCP Client MRTR Conformance (inputRequests Provenance Boundary and the resultType Default)

mcp-client-mrtr-conformance is a high severity check in the ai category, written in python. Its source is templates/ai/mcp/client-conformance/mcp-client-mrtr-conformance.py in cert-x-gen-templates.

What it checks

ACTIVE check. Drives an MCP CLIENT against one benign synthetic MCP server and proves, by observation, that it fails two 2026-07-28 client MUSTs - it lets a server-supplied inputRequests prompt cross into its own context or its own actions with nothing naming where the text came from, and it does not treat a result with an absent resultType as "complete".

There is a playbook for this check

MCP client MRTR conformance (inputRequests provenance & the resultType default) sets out the use case, the probe flow, the oracle, and the fixture that proves it in both directions.

Header

Field	Value
Id	mcp-client-mrtr-conformance
Severity	high
Language	python
Category	ai
Author	Bugb Research
Template version	1.0.0
Confidence	90
CVSS	8.2
Weakness	CWE-346, CWE-1289
Tags	mcp, ai, agent, mcp-client, mcp-client-conformance, agent-posture, mrtr, input-requests, elicitation, prompt-injection, provenance, result-type, behavioural, active, intrusive, cwe-346, cwe-1289
Target kind	cli
Oracle	property, diff

Conventions of the repository, not fields the engine reads

@target_kinds and @oracles are documented in the templates repository’s contribution guide, and cxg’s annotation parser does not carry them into a template’s metadata. Nothing at scan time selects on them. The annotation header schema is every field the parser does read.

References

Declared in the header. cxg parses @references and then discards it, and nothing at scan time reads it, so this is the only place the links a template cites are surfaced.

• https://modelcontextprotocol.io/specification/2026-07-28/basic/patterns/mrtr
• https://modelcontextprotocol.io/specification/2026-07-28/basic
• https://modelcontextprotocol.io/specification/2026-07-28/client/elicitation
• https://modelcontextprotocol.io/specification/2026-07-28/server/tools
• https://cwe.mitre.org/data/definitions/346.html
• https://cwe.mitre.org/data/definitions/1289.html

Run it

To see what the copy on your machine says about itself, and to confirm it is installed at all:

cxg template info mcp-client-mrtr-conformance

The id it prints is the one to pass anywhere a template is selected. See cxg template for the rest of the subcommand, Scan a target for running a scan, and A match is not a finding for how to read what comes back.

Related

• Template catalog is the whole corpus.
• ai is the rest of this category.
• Templates by weakness class groups checks by the defect they look for.
• Contribute a template is the route from a check you needed and could not find to a merged one.