We run a prime directive on this stack: if a usable tool already exists, improve it; build our own only as a last resort, and when you keep your own, record why each alternative failed. This post is that audit for weather-mcp — a marine-weather MCP server — against the weather-MCP ecosystem, and the one capability change that fell out of it.
The short version: three perfectly good weather MCP servers exist, and none of them does the thing a navigator actually needs. The reasons generalize to any "adopt an MCP server or keep your own" call, so the audit is the post. Then the fix — parsing a second NDBC file format to split swell from wind waves — is small enough to paste in full, and it surfaced data the standard file had thrown away.
The problem, as you'd search it
You want an agent to answer "what are the seas doing where we are?" and you go looking for a marine weather MCP. You find a few. Each one returns a forecast. None of them returns what a buoy 12 nautical miles away is measuring right now. That gap — forecast vs. observed — is the entire job, and it's the one thing the ecosystem skips.
Here's what's on the shelf, and what each one is missing for marine use.
