That aside, the MCP middleman in this case provides a few things:
1. Most importantly, it models and enforces the complex domains of the API and underlying data in a way that most people can't easily, so it maps English requests to sensible queries effortlessly. Claude uses discovery endpoints and constructs queries in seconds, is instructed to check parameters about each endpoint, and generally handles a lot of domain-specific concerns that users typically won't have a full grasp of.
Imagine a sensor network with dozens of stations and thousands of sensors. Which one should you query, for which type of data? What parameters does it take? How granular is the data? These are easy to keep track of if you're familiar with the station and have some API requests on hand that you lean on frequently. It's much harder when you want to know things about an area or type of sensor data you're less familiar with. The MCP server solves for this quite well. You can write things like "How much chlorophyll was in the ocean in the summer months of 2025 near Victoria, BC?" and it can map that to stations, then to sensors (some named chlorophyll, some named fluorometers, some named after the manufacturer's model name, etc). And yes, this can be done with a skill, but my experimentation with this was disappointing. The MCP server provides far more consistent results.
2. Less important, but the API doesn't presently differentiate between users. They have access or they don't. The writable endpoints should not be accessible to Claude, so handing it a token is not acceptable. The MCP server ensures Claude's use of the token is limited. This takes less work than rebuilding auth for the API. We could use a read-only proxy instead, but on its own, this wouldn't help my team much.
3. The API already does return consistent results. The problem lies more in the direction of knowing how to query it.
I suppose a followup point is that the code driving the MCP server is testable and provides some guarantees about the system's behaviour, which allowed me to progressively improve its end results and determinism. I don't know how to do that with skills. I'm also solving a problem for less technical users, so I can't set them loose with a skill and a terminal to begin with.