# Source: https://modelcontextprotocol.io/community/sdk-tiers.md

> ## Documentation Index
> Fetch the complete documentation index at: https://modelcontextprotocol.io/llms.txt
> Use this file to discover all available pages before exploring further.

# SDK Tiering System

> Feature completeness, protocol support, and maintenance commitment levels for Model Context Protocol SDKs

The MCP SDK Tiering System establishes clear expectations for feature completeness, protocol support, and maintenance commitments across official and community-driven SDKs. This helps developers choose the right SDK for their needs and provides SDK maintainers with a clear path to improving adoption expectations.

<Note>
  **Key dates:**

  * **January 23, 2026**: Conformance tests available
  * **February 23, 2026**: Official SDK tiering published

  Between January 23 and February 23, SDK maintainers can work with the
  Conformance Testing working group to adopt the tests and set up GitHub issue
  tracking with the standardized labels defined below.
</Note>

## Overview

SDKs are classified into three tiers based on feature completeness, maintenance commitments, and documentation quality:

* **Tier 1**: Fully supported SDKs with complete protocol implementation, including all
  non-experimental features and optional capabilities like sampling and elicitation
* **Tier 2**: Actively-maintained SDKs working toward full protocol specification support
* **Tier 3**: Experimental, partially implemented, or specialized SDKs

Experimental features (such as Tasks) and protocol extensions (such as MCP Apps) are not required
for any tier.

## Tier Requirements

| Requirement                 | Tier 1: Fully Supported                                                                  | Tier 2: Commitment to Full Support                               | Tier 3: Experimental   |
| --------------------------- | ---------------------------------------------------------------------------------------- | ---------------------------------------------------------------- | ---------------------- |
| **Conformance Tests**       | 100% pass rate                                                                           | 80% pass rate                                                    | No minimum             |
| **New Protocol Features**   | Before new spec version release, timeline agreed per release based on feature complexity | Within 6 months                                                  | No timeline commitment |
| **Issue Triage**            | Within 2 business days                                                                   | Within a month                                                   | No requirement         |
| **Critical Bug Resolution** | Within 7 days                                                                            | Within two weeks                                                 | No requirement         |
| **Stable Release**          | Required with clear versioning                                                           | At least one stable release                                      | Not required           |
| **Documentation**           | Comprehensive with examples for all features                                             | Basic documentation covering core features                       | No minimum             |
| **Dependency Policy**       | Published update policy                                                                  | Published update policy                                          | Not required           |
| **Roadmap**                 | Published roadmap                                                                        | Published plan toward Tier 1 or explanation for remaining Tier 2 | Not required           |

**Issue Triage** means labeling and determining whether an issue is valid, not resolving the issue.

**Critical Bug** refers to P0 issues (see [Priority labels](#priority-only-if-actionable) for
detailed criteria).

**Stable Release** is a published version explicitly marked as production-ready (e.g., version `1.0.0`
or higher without pre-release identifiers like `-alpha`, `-beta`, or `-rc`).

**Clear Versioning** means following idiomatic versioning patterns with documented
breaking change policies, so users can understand compatibility expectations when upgrading.

**Roadmap** outlines concrete steps and work items that track implementation of required MCP
specification components (non-experimental features and optional capabilities as described in
[Conformance Testing](#conformance-testing)), giving users visibility into upcoming feature support.

## Conformance Testing

All SDKs are evaluated using [automated conformance tests](https://github.com/modelcontextprotocol/conformance)
that validate protocol support against the published specifications. SDKs receive a conformance score
based on test results:

* **Tier 1**: 100% conformance required
* **Tier 2**: 80% conformance required
* **Tier 3**: No minimum requirement

Conformance scores are calculated against **applicable required tests** only:

* Tests for the specification version the SDK targets
* Excluding tests marked as pending or skipped
* Excluding tests for experimental features
* Excluding legacy backward-compatibility tests (unless the SDK claims legacy support)

Conformance testing validates that SDKs correctly implement the protocol by running standardized test
scenarios and checking protocol message exchanges. See [Tier Relegation](#tier-relegation) for how
temporary test failures are handled.

## Tier Advancement

SDK maintainers can request tier advancement by:

1. Self-assessing against tier requirements
2. Opening an issue in the [modelcontextprotocol/modelcontextprotocol](https://github.com/modelcontextprotocol/modelcontextprotocol) repository with supporting evidence
3. Passing automated conformance testing
4. Receiving approval from SDK Working Group maintainers

The SDK Working Group reviews advancement requests and makes final tier assignments.

## Tier Relegation

An SDK may be moved to a lower tier if existing conformance tests on the latest stable release fail
continuously for 4 weeks:

* **Tier 1 → Tier 2**: Any conformance test fails
* **Tier 2 → Tier 3**: More than 20% of conformance tests fail

## Issue Triage Labels

SDK repositories must use consistent labels to enable automated reporting on issue handling metrics.
Tier calculations use these metrics to measure triage response times (time from issue creation to
first label) and critical bug resolution times (time from P0 label to issue close).

### Type (pick one)

| Label         | Description                   |
| ------------- | ----------------------------- |
| `bug`         | Something isn't working       |
| `enhancement` | Request for new feature       |
| `question`    | Further information requested |

Repositories using [GitHub's native issue types](https://docs.github.com/en/issues/tracking-your-work-with-issues/using-issues/managing-issue-types-in-an-organization)
satisfy this requirement without needing type labels.

### Status (pick one)

Use these exact label names across all repositories to enable consistent reporting and analysis.

| Label                | Description                                             |
| -------------------- | ------------------------------------------------------- |
| `needs confirmation` | Unclear if still relevant                               |
| `needs repro`        | Insufficient information to reproduce                   |
| `ready for work`     | Has enough information to start                         |
| `good first issue`   | Good for newcomers                                      |
| `help wanted`        | Contributions welcome from those familiar with codebase |

### Priority (only if actionable)

| Label | Description                                                     |
| ----- | --------------------------------------------------------------- |
| `P0`  | Critical: core functionality failures or high-severity security |
| `P1`  | Significant bug affecting many users                            |
| `P2`  | Moderate issues, valuable feature requests                      |
| `P3`  | Nice to haves, rare edge cases                                  |

**P0 (Critical)** issues are:

* **Security vulnerabilities** with CVSS score ≥ 7.0 (High or Critical severity)
* **Core functionality failures** that prevent basic MCP operations: connection establishment,
  message exchange, or use of core primitives (tools, resources, prompts)