Building With MCP: Tool Standards for Agent Interoperability
The Model Context Protocol is becoming the standard for how agents discover and call tools. What it changes and what it does not.
Every agent framework reinvents tool calling: custom schemas, custom registries, custom error handling. The Model Context Protocol (MCP) is an attempt to standardize this — a protocol for how an agent discovers a tool's schema, calls it, and receives results. It is not a framework; it is a contract.
What MCP standardizes
MCP standardizes three things: tool discovery (an agent can list available tools and their schemas), tool invocation (a standard request/response format), and tool errors (a standard error vocabulary). This means an agent built for one MCP-compatible tool server can talk to any other without custom integration code.
What it does not solve
MCP does not solve tool selection — the agent still decides which tool to call. It does not solve authorization — the server still decides whether the caller may call the tool. And it does not solve idempotency — the tool still decides whether a repeat call is safe. MCP is the transport layer; the intelligence is still in the agent.
Writing a good tool spec
An MCP tool spec is a JSON Schema for the input and output. A good spec is narrow: required fields are truly required, constraints are explicit (max length, regex, enum), and the description tells the agent when to call this tool vs. an alternative. A vague spec produces vague tool calls.
The interop win
The real value of MCP is not any single tool — it is that tools become interchangeable. You can swap a file-search tool for a database-query tool without rewriting the agent. The agent calls 'search' and does not care whether the backend is a vector DB or a grep. This separation is what makes agent systems maintainable.
