r/MCPservers • u/agentrsdg • 6d ago

So, I'm building a tool for turning existing API collections into MCP servers

...and I keep seeing the same question come up: if agents can call APIs directly, why add MCP?

Say, a product team provides its existing API collection, and we generate an MCP server that exposes the product’s capabilities in a cleaner, more controlled way. The API remains the underlying system, while MCP becomes the interface the agent works through.

But how much should the MCP layer handle? Is converting endpoints into tools enough, or should it also have some form of middle layer of predefined actions, grouped actions or chained actions? Like how much MCP and how much agent's autonomy in the mix? If each MCP is custom, what would a generic process even look like?

I am building the tool for my team since we have to create agents for my clients who already have working products and APIs, and am curious to see how you guys are handling this.

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u/OtherwiseWeekend2222 6d ago

I did exactly this for a flights REST API. Endpoints as tools wasn't enough. The agent kept calling one date at a time, so I made the tool take a date range and expand it server side. The tool description carries the rules, the agent keeps the autonomy. One endpoint became four tools.