MCP Servers: A Builder's Field Guide
Model Context Protocol servers let agents talk to your systems without brittle plugins. Here is how to design one worth installing.
MCP servers are the new integration surface for agents. They are small, focused, and designed to be discovered at runtime. Ship one and your work becomes usable by every serious agent stack in the ecosystem.
This guide is for builders who want their MCP server to feel obvious the first time an agent tries to use it.
Design for discovery
Every tool needs a plain-English description. Agents pick tools by reading their docs, so treat that copy like a landing page.
- Say what the tool does in one line.
- Say when to use it and when not to.
- Give a one-line example of the input and output.
Fail with useful errors
When a tool call fails, return a message the model can act on. 'Missing field: customer_id' beats a 500.
The best MCP servers are the ones that teach the agent how to use them through their error messages.
Keep the surface tiny
Ten well-named tools beat a hundred fine-grained ones. Agents pick tools by name; if your names are close to each other, they will pick wrong.
Publish with real examples
Ship a README with three example calls and their responses. Buyers install what they can immediately test.
Version your schema
Breaking changes in an MCP schema silently break every agent using it. Version the schema, publish a migration note, and support the previous version for at least a quarter.
Get these five right and your MCP server will show up in agent stacks you never marketed to. That is the whole point.
