Engineering Lessons from Building 40 MCP Servers
Background-Job-862 · reddit · 2026-07-14
The author reviews typical pitfalls encountered after building about 40 MCP servers, focusing on engineering implementation rather than concepts.
Key takeaways include:
- Avoid hand-writing too many server wrappers: Writing a separate server for each internal API doesn't scale. They later switched to converting OpenAPI specs directly into MCP tools, cutting server setup time from a full day to under an hour.
- Keep tool granularity moderate: Too fine-grained wastes model context, while too coarse leads to incorrect parameter filling. Ultimately, categorizing by "user intent" rather than underlying endpoints works best.
- Design error messages for the model: Structured, interpretable error prompts significantly reduce the agent's repeated retries on failed calls.
- Unify authentication and credentials: Custom-built servers often end up with different auth logic per service, leading to credential sprawl.
Finally, they migrated new server creation to Truefoundry's tools, leveraging OpenAPI-to-MCP conversion and managed stdio servers to handle authentication uniformly.
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