SHEARLINE

The severe-weather analyst your agent doesn't have. SHEARLINE is a free, MIT-licensed MCP server that gives AI agents analyst-grade US severe-weather tools: live warning polygons with Impact-Based Warning tags, SPC convective outlooks, RAP-derived point environments and forecast trends (CAPE/shear/SRH/STP computed with MetPy), MRMS radar-derived hail and rotation products, GOES lightning, ground-truth storm reports (real-time and historical), and a composite threat brief that synthesizes all of it. A dozen weather MCPs already wrap the basic forecast API; SHEARLINE deliberately skips everything they do and ships only what requires radar meteorology to expose correctly.

Informational only. Not a substitute for official NWS warnings. Every tool repeats this, because it matters: when weather threatens, follow official warnings from weather.gov and local authorities.

Tools

Every tool returns structured JSON with data (numeric fields, units stated), interpretation (plain-language analyst sentences), degraded (which upstream sources failed, if any — partial data instead of errors), the safety disclaimer, and a schema_version — the field contract is semver-stable (see ARCHITECTURE), so integrators can depend on it.

Example: threat brief during a real outbreak

Real output from 2026-06-10, point inside an active tornado warning in northern Missouri:

{
  "threat_level": "extreme",
  "threat_logic": [
    "Tornado Warning in effect at the point, corroborated by confirmed tornado reports nearby — treat as an immediate life-safety situation.",
    "Severe Thunderstorm Warning at the point tagged 'Considerable' (hail to 1.75\", gusts to 60 mph).",
    "Significant-tornado parameter of 4.0 with storms ongoing — environment strongly supports tornadic supercells.",
    "MRMS MESH of 2.3\" hail within radius in the last hour.",
    "Intense rotation track (azimuthal shear 0.013 /s) nearby in the last hour.",
    "6 tornado report(s) near the point in the report window."
  ],
  "hazards_ranked": [
    {"hazard": "tornado", "level": "extreme"},
    {"hazard": "hail", "level": "extreme"},
    {"hazard": "damaging_wind", "level": "extreme"},
    {"hazard": "flash_flood", "level": "moderate"}
  ],
  "nearest_storm_signature": {
    "signature": "composite reflectivity", "value": "58.5 dBZ",
    "distance_km": 18.0, "direction": "ENE", "valid_utc": "2026-06-10T22:14Z"
  },
  "attention_window": {"window": "now", "until_utc": "2026-06-10T21:00:00-05:00"}
}

And the same tool for a quiet coastal Maine point reads as confidently quiet — not as an error: "threat_level": "none" with the environment numbers shown so the agent can see why it's quiet.

Install

Requires Python 3.12+ and uv. No API keys — every data source is public and anonymous. uvx downloads and runs the published package in one step; nothing is installed permanently.

Claude Code:

claude mcp add shearline -- uvx shearline

Claude Desktop (claude_desktop_config.json):

{
  "mcpServers": {
    "shearline": {
      "command": "uvx",
      "args": ["shearline"]
    }
  }
}

Streamable HTTP (for remote/agent-platform use):

uvx shearline --http --port 8741
# serves at http://127.0.0.1:8741/mcp

On macOS you can also double-click scripts/launch.command to start the HTTP server in a Terminal window (honours SHEARLINE_PORT).

The HTTP transport is built to be hosted: it emits one structured JSON log line per tool call (tool, coarse 1° lat/lon bucket, latency, degraded list, cache hit/miss) and applies a per-client token-bucket rate limit, returning 429 with Retry-After when exceeded. Both are HTTP-only — stdio behaviour is unchanged. Configure via environment variables:

To run the latest unreleased main instead of the PyPI release, swap shearline for --from git+https://github.com/lostnumber07/shearline shearline.

Why these tools

A forecast API tells you it might rain. None of the questions that matter on a severe weather day — is this storm rotating, how big is the hail, is the environment loaded for tornadoes, am I inside the polygon — are answerable from a forecast endpoint. They require the warning's IBW tags, radar-derived products, and a real sounding: