DEV Community: Wannavf The latest articles on DEV Community by Wannavf (@wannavf). https://dev.to/wannavf https://media2.dev.to/dynamic/image/width=90,height=90,fit=cover,gravity=auto,format=auto/https:%2F%2Fdev-to-uploads.s3.amazonaws.com%2Fuploads%2Fuser%2Fprofile_image%2F3917730%2F8db35a4f-5906-4406-84d5-d32f2a755cd5.png DEV Community: Wannavf https://dev.to/wannavf en My MCP Tools Broke Silently; So I Built a Lockfile for MCP Wannavf Thu, 07 May 2026 11:00:49 +0000 https://dev.to/wannavf/my-mcp-tools-broke-silently-so-i-built-a-lockfile-for-mcp-2dah https://dev.to/wannavf/my-mcp-tools-broke-silently-so-i-built-a-lockfile-for-mcp-2dah <h2> The Problem </h2> <p>I run AI agents that depend on MCP servers. One morning, everything broke. No error message. No warning. Just silent failures.</p> <p>After 4 hours of debugging, I found it: the MCP server updated and renamed a parameter from <code>location</code> to <code>city</code>. My agent was still sending <code>location</code>. The server returned a cryptic <code>-32602</code> error.</p> <p>The MCP spec has 9,400+ servers and 97 million SDK downloads per month. But it has <strong>zero per-tool versioning</strong>. When a server changes its tool schemas, nothing tells you what changed or whether it matters.</p> <h2> What I Built </h2> <p><strong>MCP Sentinel</strong> a lockfile for MCP servers. Think <code>package-lock.json</code>, but for MCP tool schemas.<br> </p> <div class="highlight js-code-highlight"> <pre class="highlight shell"><code>npm <span class="nb">install</span> <span class="nt">-g</span> @wannavf/mcp-sentinel sentinel init <span class="c"># Setup wizard</span> sentinel snapshot <span class="c"># Lock current schemas</span> sentinel check <span class="c"># Detect drift → exit code for CI</span> sentinel diff <span class="c"># See exactly what changed</span> </code></pre> </div> <p><strong>GitHub:</strong> <a href="https://github.com/Wannavf/mcp-sentinel" rel="noopener noreferrer">github.com/Wannavf/mcp-sentinel</a><br> <strong>npm:</strong> <code>npm install -g @wannavf/mcp-sentinel</code><br> <strong>License:</strong> MIT</p> <p>Issues and PRs welcome.</p> ai mcp devtools opensource