---
title: "Client conformance checklist"
description: "This checklist is non-normative. The [complete specification](/spec) governs when wording differs."
canonical: https://agentpluginsdirectory.com/spec/client-implementers/conformance
last-updated: 2026-09-21
---

# Client conformance checklist

This checklist is non-normative. The [complete specification](/spec) governs when wording differs.

## Plugin loader
* [ ] Load a plugin from a directory and enforce the filesystem-resolved package boundary.
* [ ] Select locally supported manifest rules from `$schema`; do not retrieve a schema during loading.
* [ ] Validate the closed `plugin.json` schema and required `$schema` and `name` fields.
* [ ] Report and ignore unknown top-level fields.
* [ ] Ignore a non-object `extensions` field and unimplemented extension namespaces.
* [ ] Reject other fatal manifest violations before component discovery.

## Discovery and isolation
* [ ] Discover supported component types only from their fixed locations.
* [ ] Treat missing component locations as valid absence.
* [ ] Isolate invalid component types, skills, and MCP entries at their specified boundaries.
* [ ] Ignore unsupported component types and support at least one of skills or MCP servers.

## MCP support
* [ ] If MCP is implemented, support at least one of stdio and Streamable HTTP; support for both is recommended.
* [ ] Use each server entry's declared transport for the initial connection attempt.
* [ ] Validate the closed top-level document and each server entry independently.
* [ ] Resolve stdio commands as single executable tokens.
* [ ] Provide `PLUGIN_ROOT` and a dedicated persistent `PLUGIN_DATA` directory.
* [ ] Expand only the two defined placeholders and only in `args`, `env` values, and `cwd`.
* [ ] Enforce working-directory containment and remote URL/header requirements.
* [ ] Continue loading after an independent MCP server fails.

## Versioning
* [ ] Require matching Agent Plugins versions in `plugin.json` and `mcp.json`.
* [ ] Never reassign a published canonical schema identifier to different contents.
* [ ] Allow plugins to continue targeting older versions according to locally supported compatibility policy.