"The engineering problem was less simple: How do you make that workflow useful without creating an unsafe bridge between an LLM and production data? That question shaped the implementation from the beginning. We did not treat the MCP server as a convenience wrapper around an existing API. We treated it as a first-class interface with its own"
"Separating read and write operations at the tool level is one of the simplest and most effective ways to reduce risk in LLM-connected systems. A default-deny approach to mutations creates a safer path from experimentation to production use."
"Mocked tests became much more valuable once we captured the actual GraphQL variables sent by each tool, which exposed normalization bugs such as incorrect country-code resolution and missing limit capping before requests reached AppSync."
"The most important production failure in the project was not caught by unit tests such as create_collection, which passed mocked tests but failed against the real backend with a Lambda null-pointer error. This situation is why real-system validation through MCP Inspector remained a release gate."
An MCP server was built to let users query a B2B intelligence platform through an LLM client, returning structured results such as “find SaaS companies in Germany with 50-200 employees.” The server was treated as a first-class production interface rather than a thin wrapper around existing APIs. Read and write operations were separated at the tool level to reduce risk in LLM-connected systems. Mutations used a default-deny approach to create a safer path from experimentation to production. Mocked tests became more valuable after capturing the actual GraphQL variables sent by each tool, which exposed normalization bugs and missing limit capping before requests reached AppSync. A key production failure involved a Lambda null-pointer error not caught by mocked unit tests, making real-system validation through MCP Inspector a release gate.
#model-context-protocol #llm-to-production-safety #graphql #tool-design-readwrite-separation #testing-and-validation
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