What is the MCP Spec Checker?

It is a specialized tool for Claude Code that performs semantic analysis and validation of Model Context Protocol (MCP) specifications to ensure compliance across different versions.

Can I use this for debugging MCP messages?

Yes, it can generate minimal counterexamples—messages that pass one spec version but fail another—to help you pinpoint exactly where your implementation needs fixing.

Which MCP versions are supported?

The skill is pre-configured to handle comparisons and migrations between the 0618 (June 2024) and 1125 (November 2025) specs, but can be applied to any predicate-level protocol definition.

What is the benefit of the triadic verification approach?

By using Narya types, GF(3) evaluators, and Unison effects, the skill ensures that three independent methodologies agree on a message's validity, providing high-confidence protocol verification.

How does it detect breaking changes between MCP versions?

It uses a semantic diff engine that compares invariants and predicates rather than just text, allowing it to find logic-level incompatibilities between versions like 0618 and 1125.

MCP Spec Checker

Name: MCP Spec Checker
Author: plurigrid

byplurigrid

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API Development

Performs predicate-level semantic diffing and cross-validation for Model Context Protocol (MCP) specifications to detect breaking changes and ensure protocol compliance.

The MCP Spec Checker is a sophisticated verification engine designed to manage the evolution of Model Context Protocol specifications. By utilizing a triadic verification approach—combining Narya bidirectional typing, GF(3) predicate evaluators, and Unison-style algebraic effects—it provides a mathematically rigorous way to identify semantic differences between protocol versions (such as 0618 and 1125). This skill is essential for developers building MCP-compliant tools or servers, enabling them to migrate versions seamlessly, verify message integrity, and generate minimal counterexamples for protocol incompatibilities to ensure implementation robustness.

Key Features

01Semantic Diffing: Identifies logic-level changes between protocol versions beyond simple text comparisons.

022 GitHub stars

03Triadic Verification: Uses three independent approaches (Narya, GF(3), Unison) for consensus-based validation.

04Counterexample Generation: Automatically produces minimal message examples that highlight protocol incompatibilities.

05Version Migration: Simplifies the transition between MCP spec versions (e.g., June 2024 to November 2025).

06Trace Validation: Validates entire protocol interaction logs against specific specification requirements.

Use Cases

01Debugging protocol handshake failures by generating minimal failing message examples for troubleshooting.

02Verifying that a custom tool implementation strictly adheres to latest MCP schema requirements.

03Migrating an MCP server implementation from version 0618 to the 1125 specification.

What are Skills?·How to Install

Install with 🐟 Skill.Fish

npx skillfish add plurigrid/asi mcp-spec-checker

For use in Claude.ai and ChatGPT

Download Skill