Add input_cost_trend / input_cost_series MCP tools (EIA diesel)

Real input price + WoW/YoY change + seasonal for diesel ($/gal). Formatters now
handle the item/label payload shape. Changelog updated.

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

ag_bids_mcp/server.py

@@ -303,6 +303,42 @@ def price_series(
         return fmt.fmt_price_series(payload)
 
 
+VALID_INPUTS = {"diesel"}
+
+
+@mcp.tool()
+def input_cost_trend(
+    item: Annotated[
+        str, Field(description="Input to price. Currently: 'diesel' (U.S. retail $/gal).")
+    ],
+    years: Annotated[
+        int, Field(ge=1, le=120, description="Baseline window for the seasonal normal/percentile."),
+    ] = 10,
+) -> str:
+    """Real input cost with the change — e.g. U.S. retail diesel ($/gal).
+
+    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."""
+    it = item.strip().lower()
+    with track("input_cost_trend", item=it, 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))
+
+
+@mcp.tool()
+def input_cost_series(
+    item: Annotated[str, Field(description="Input: 'diesel'.")],
+) -> str:
+    """Raw historical series for a tracked input cost (diesel, $/gal)."""
+    it = item.strip().lower()
+    with track("input_cost_series", item=it):
+        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))
+
+
 @mcp.tool()
 def list_sources() -> str:
     """All active scrapers + their last-success timestamps and any pending failures."""