Add fertilizer to input-cost tools (regional $/ton, USDA AgTransport)

input_cost_trend/input_cost_series now accept six fertilizers (urea, uan,
anhydrous, dap, map, potash) alongside diesel, with an optional `geo` region
(default Cornbelt). Real $/ton + MoM/YoY change + seasonal context.

- client: pass geo through; add input_cost_geographies
- server: expand VALID_INPUTS; geo param + docstrings
- format already unit-aware ($/ton) and geo-aware
- README tools table now lists the reference/trend + input-cost tools
- CHANGELOG: regional fertilizer input-cost release notes
- tests: fertilizer $/ton + region formatting

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

ag_bids_mcp/server.py

@@ -303,40 +303,61 @@ def price_series(
         return fmt.fmt_price_series(payload)
 
 
-VALID_INPUTS = {"diesel"}
+# Fuel is national (US); fertilizer is regional ($/ton, USDA AgTransport).
+VALID_INPUTS = {"diesel", "urea", "uan", "anhydrous", "dap", "map", "potash"}
+_FERT_INPUTS = {"urea", "uan", "anhydrous", "dap", "map", "potash"}
 
 
 @mcp.tool()
 def input_cost_trend(
     item: Annotated[
-        str, Field(description="Input to price. Currently: 'diesel' (U.S. retail $/gal).")
+        str,
+        Field(description="Input to price: 'diesel' (U.S. retail $/gal) or a fertilizer "
+                          "($/ton) — 'urea', 'uan', 'anhydrous', 'dap', 'map', 'potash'."),
     ],
+    geo: Annotated[
+        str | None,
+        Field(description="Fertilizer region (default 'Cornbelt'). Other regions: "
+                          "'U.S. Gulf NOLA', 'Northern Plains', 'Southern Plains', "
+                          "'Southeast', 'Northeast', 'California', 'Pacific Northwest', "
+                          "'South Central', 'Central Florida', 'Tampa'. Ignored for diesel (US)."),
+    ] = None,
     years: Annotated[
         int, Field(ge=1, le=120, description="Baseline window for the seasonal normal/percentile."),
     ] = 10,
 ) -> str:
-    """Real input cost with the change — e.g. U.S. retail diesel ($/gal).
+    """Real input cost with the change — retail diesel ($/gal) or fertilizer ($/ton).
 
-    Latest real price + week-over-week and year-over-year moves + seasonal
-    percentile/range. Fills the input-cost side for the advisor (fuel). For
-    current fertilizer $/ton use current_input_price."""
+    Latest real price + period-over-period and year-over-year moves + seasonal
+    percentile/range. Diesel is U.S. weekly (back to 1994); fertilizer is monthly
+    regional (USDA AgTransport, Cornbelt default, back to 2023). This is the
+    input-cost side for the advisor. For a one-off current fertilizer quote from a
+    local dealer feed, current_input_price (DTN) still applies."""
     it = item.strip().lower()
-    with track("input_cost_trend", item=it, years=years):
+    g = geo.strip() if geo else None
+    with track("input_cost_trend", item=it, geo=g or "", years=years):
         if it not in VALID_INPUTS:
             return f"`item` must be one of: {sorted(VALID_INPUTS)}"
-        return fmt.fmt_price_trend(client.input_cost_trend(item=it, years=years))
+        return fmt.fmt_price_trend(client.input_cost_trend(item=it, years=years, geo=g))
 
 
 @mcp.tool()
 def input_cost_series(
-    item: Annotated[str, Field(description="Input: 'diesel'.")],
+    item: Annotated[
+        str, Field(description="Input: 'diesel' or a fertilizer ('urea', 'uan', "
+                              "'anhydrous', 'dap', 'map', 'potash').")],
+    geo: Annotated[
+        str | None,
+        Field(description="Fertilizer region (default 'Cornbelt'). Ignored for diesel."),
+    ] = None,
 ) -> str:
-    """Raw historical series for a tracked input cost (diesel, $/gal)."""
+    """Raw historical series for a tracked input cost (diesel $/gal or fertilizer $/ton)."""
     it = item.strip().lower()
-    with track("input_cost_series", item=it):
+    g = geo.strip() if geo else None
+    with track("input_cost_series", item=it, geo=g or ""):
         if it not in VALID_INPUTS:
             return f"`item` must be one of: {sorted(VALID_INPUTS)}"
-        return fmt.fmt_price_series(client.input_cost_series(item=it))
+        return fmt.fmt_price_series(client.input_cost_series(item=it, geo=g))
 
 
 @mcp.tool()