What I check when I review an MCP server
An MCP server gives an AI client a callable interface. Reviewing it means following the path from a tool description to the code that reads data, changes state, or authorizes a payment. I want the interface to explain that behavior accurately, including what happens when a request fails. These examples come from two public projects: textokit-mcp and dotnet-mcp-orders-server. The pinned textokit…
When reviewing an MCP server, I examine four key aspects: interface accuracy, descriptions, failure handling, and secret management. Beginning with the interface, I ensure that the tool names and input schemas match the implementation, paying close attention to the transformation process. The descriptions should clearly define the tool's boundaries, avoiding false promises of capabilities that the implementation does not provide.
For failure and timeout scenarios, I search for explicit error responses and time limits, examining how the server differentiates between unsuccessful requests and successful ones containing error messages. I also investigate the handling of sensitive information, tracing credentials from configuration into sensitive areas like signing and authentication, ensuring that secrets are not exposed in logs or outputs.
Lastly, for operations with significant consequences, such as spending or making changes, I verify that proper authorization mechanisms are in place, beyond simply passing pre-approved arguments. This thorough examination ensures that the MCP server operates correctly and securely.
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