Build Your First MCP Server

The route

4 steps to Done

1. 01

   Choose tools worth exposing and set up the SDK

   A first server succeeds by doing few things properly.

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   Plan the server. Choose 2-3 tools that are genuinely useful and safely scoped for a first server - good candidates: a project-search tool (query in, ranked hits out), a read-only data lookup from my domain, and one bounded action tool. For each, write the name, steering description, and JSON schema (apply tight-schema practice: enums, ranges, additionalProperties false). Install the official MCP SDK for my language (verify the current package name and API from the official docs - the ecosystem moves fast) and scaffold the server project with the SDK's canonical structure.

   • ✓ Tools are useful, bounded, and schema-tight
   • ✓ Official SDK installed and current
   • ✓ Scaffold follows SDK conventions
2. 02

   Implement the server and tools

   Register, validate, execute, respond - the whole job.

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   Implement the MCP server. Register each tool with its schema and description; implement handlers that validate inputs server-side (even though schemas exist - defense in depth), execute the real logic, and return results as proper MCP content; convert every handler exception into a structured tool error result (never let it crash the transport); add logging of every call: tool, arguments, duration, result size or error. Choose the transport per my deployment: stdio for local host integration, HTTP/SSE-style for remote per current spec guidance. Start the server and confirm it initializes cleanly.

   • ✓ Handlers validate independently of schema
   • ✓ Exceptions become error results
   • ✓ Every call logged with duration
3. 03

   Connect a host and verify discovery

   The protocol is only real once a host you did not write speaks it.

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   Connect the server to a real MCP host (an MCP-capable IDE/agent, or a general client library like mcp-use if scripting the client). Configure the host to launch/reach the server; verify initialization completes; list tools from the host side and check names, descriptions, and schemas arrive intact (serialization bugs show up here). Then invoke each tool from the host with valid arguments and confirm results render correctly. Capture the server logs during this session as the discovery-verification record.

   • ✓ Initialization handshake completes
   • ✓ Schemas arrive intact host-side
   • ✓ All tools callable from the host
4. 04

   Test errors and edge behavior through the protocol

   Error paths are where integrations actually break.

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   Exercise the failure modes through the host. Send: invalid arguments (schema violation) - expect a readable protocol error, server alive; arguments valid to schema but failing handler validation - expect a structured tool error explaining why; a tool call that takes long - verify timeout behavior on both sides and pick sane server-side limits; oversized results - add a result-size cap with truncation notes if any tool can produce large output. After each case, confirm the server continues serving subsequent calls. Document the server's error contract (what callers can expect) in the README.

   • ✓ Schema and handler errors both readable
   • ✓ Timeouts bounded on the server side
   • ✓ Result-size cap in place

Research-backed

Sources behind this flow