Error visibility and agent tool cleanup

Exchange-rate fetchers log every source failure instead of silently
passing (BE-18); the rate tool exposes fetched_at so staleness is
visible (BE-20). Agent: unbound-session failures raise a clear
RuntimeError (BE-12); net worth converts via get_crc_multipliers with
last-known fallbacks instead of a hardcoded 600 CRC / 1.08 EUR guess,
and reports accounts it cannot convert rather than inventing numbers
(BE-24); budget tool enforces MIN/MAX_YEAR (BE-16); municipal receipts
gain offset paging (BE-17); category analytics prefetches names; the
module docstring pins the read-only tool policy (SEC-09). Note: the
refresh loop never swallowed CancelledError (BaseException since 3.8) —
ARCH-08 was a false positive.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

backend/app/agent/tools.py

@@ -3,6 +3,11 @@ Read-only tools exposed to the MAF ChatAgent. Each tool is a thin wrapper
 around existing SQLModel queries / service helpers — they do NOT duplicate
 business logic. The active DB session is resolved via a ContextVar so tool
 signatures stay clean for the LLM.
+
+POLICY: every tool here must stay READ-ONLY. Transaction descriptions reach
+the model from external emails (indirect prompt-injection surface), so a
+write-capable tool would let crafted text mutate financial data. Any future
+write tool requires an explicit user-confirmation step in the UI.
 """
 
 from __future__ import annotations
@@ -28,10 +33,13 @@ from app.models.models import (
     WaterMeterReading,
 )
 from app.services.budget_projection import (
+    MAX_YEAR,
+    MIN_YEAR,
     compute_monthly_projection,
     compute_yearly_projection_with_cumulative,
     get_cycle_range,
 )
+from app.services import exchange_rate as fx
 from app.services.exchange_rate import (
     get_converted_amount_expr,
     get_current_rate,
@@ -49,7 +57,13 @@ def reset_session(token: contextvars.Token) -> None:
 
 
 def _s() -> Session:
-    return _session_ctx.get()
+    try:
+        return _session_ctx.get()
+    except LookupError as exc:
+        raise RuntimeError(
+            "DB session not bound to agent context — tool called outside an "
+            "HTTP request (the AG-UI middleware binds it per request)"
+        ) from exc
 
 
 # ─── Tools ──────────────────────────────────────────────────────────────────
@@ -77,26 +91,31 @@ def get_accounts() -> list[dict]:
 def get_net_worth() -> dict:
     """Return total assets, liabilities and net worth in CRC (primary currency).
     USD/EUR balances are converted at the latest exchange rate."""
-    accounts = _s().exec(select(Account)).all()
-    rate = get_current_rate(_s())
-    sell = float(rate.sell_rate) if rate else 600.0
+    session = _s()
+    accounts = session.exec(select(Account)).all()
+    multipliers = fx.get_crc_multipliers(session)
     assets_crc = 0.0
     liabilities_crc = 0.0
+    excluded: list[str] = []
     for a in accounts:
-        amt = float(a.balance)
-        if a.currency.value == "USD":
-            amt = float(a.balance) * sell
-        elif a.currency.value == "EUR":
-            amt = float(a.balance) * sell * 1.08  # rough; real conversion is endpoint-side
+        mult = multipliers.get(a.currency.value)
+        if mult is None:
+            # No live or last-known rate: say so instead of inventing a number
+            excluded.append(f"{a.label} ({a.currency.value})")
+            continue
+        amt = float(a.balance) * float(mult)
         if a.account_type.value == "LIABILITY":
             liabilities_crc += amt
         else:
             assets_crc += amt
-    return {
+    result = {
         "assets_crc": round(assets_crc, 2),
         "liabilities_crc": round(liabilities_crc, 2),
         "net_crc": round(assets_crc - liabilities_crc, 2),
     }
+    if excluded:
+        result["excluded_accounts_no_rate"] = excluded
+    return result
 
 
 def get_recent_transactions(
@@ -218,6 +237,8 @@ def get_budget_projection(
     """Budget projection. If month is omitted, returns the yearly rollup; if
     given, returns the monthly detail with income items, expense items and
     actuals by source."""
+    if not MIN_YEAR <= year <= MAX_YEAR:
+        return {"error": f"year must be between {MIN_YEAR} and {MAX_YEAR}"}
     session = _s()
     if month is None:
         months_data = compute_yearly_projection_with_cumulative(session, year)
@@ -322,6 +343,7 @@ def get_salary_summary() -> dict:
 
 def get_municipal_receipts(
     limit: Annotated[int, Field(ge=1, le=50)] = 12,
+    offset: Annotated[int, Field(ge=0, description="Skip the N most recent")] = 0,
     account: Annotated[
         Optional[str], Field(description="Municipal account/contract id")
     ] = None,
@@ -331,7 +353,7 @@ def get_municipal_receipts(
     q = select(MunicipalReceipt).order_by(col(MunicipalReceipt.receipt_date).desc())
     if account:
         q = q.where(MunicipalReceipt.account == account)
-    q = q.limit(limit)
+    q = q.offset(offset).limit(limit)
     rows = _s().exec(q).all()
     # One grouped query for all receipts instead of one per receipt
     consumption: dict[int, float] = {}
@@ -387,13 +409,10 @@ def get_analytics_by_category(
         q = q.where(Transaction.date >= start, Transaction.date < end)
     rows = session.exec(q).all()
     grand = sum(float(r[1]) for r in rows) or 1.0
+    names = {c.id: c.name for c in session.exec(select(Category)).all()}
     out = []
     for cat_id, total, count in rows:
-        name = "Uncategorized"
-        if cat_id:
-            cat = session.get(Category, cat_id)
-            if cat:
-                name = cat.name
+        name = names.get(cat_id, "Uncategorized") if cat_id else "Uncategorized"
         out.append(
             {
                 "category_id": cat_id,
@@ -460,6 +479,7 @@ def get_exchange_rate() -> dict:
         "buy_rate": float(rate.buy_rate),
         "sell_rate": float(rate.sell_rate),
         "date": rate.date.isoformat(),
+        "fetched_at": rate.fetched_at.isoformat() if rate.fetched_at else None,
     }
 
 

backend/app/services/exchange_rate.py

@@ -61,8 +61,8 @@ def _fetch_bccr_rate(indicator: int, date_str: str) -> float | None:
         for datos in root.iter():
             if datos.tag.endswith("NUM_VALOR"):
                 return float(datos.text.strip().replace(",", "."))
-    except Exception:
-        pass
+    except Exception as e:
+        logger.warning("BCCR rate fetch failed (indicator %s): %s", indicator, e)
     return None
 
 
@@ -91,8 +91,8 @@ def _fetch_exchangerate_api() -> tuple[float, float] | None:
             crc = data["rates"].get("CRC")
             if crc:
                 return _mid_to_buy_sell(float(crc))
-    except Exception:
-        pass
+    except Exception as e:
+        logger.warning("ExchangeRate-API fetch failed: %s", e)
     return None
 
 
@@ -106,7 +106,8 @@ def _fetch_currency_api() -> tuple[float, float] | None:
             crc = data.get("usd", {}).get("crc")
             if crc:
                 return _mid_to_buy_sell(float(crc))
-        except Exception:
+        except Exception as e:
+            logger.warning("currency-api fetch failed (%s): %s", url, e)
             continue
     return None
 
@@ -120,8 +121,8 @@ def _fetch_floatrates() -> tuple[float, float] | None:
         crc_data = data.get("crc")
         if crc_data and "rate" in crc_data:
             return _mid_to_buy_sell(float(crc_data["rate"]))
-    except Exception:
-        pass
+    except Exception as e:
+        logger.warning("FloatRates fetch failed: %s", e)
     return None
 
 
@@ -199,8 +200,8 @@ def _fetch_fiat_crc_mid(code: str) -> float | None:
             x = data["rates"].get(code)
             if crc and x:
                 return float(crc) / float(x)
-    except Exception:
-        pass
+    except Exception as e:
+        logger.warning("%s/CRC fiat rate fetch failed: %s", code, e)
     return None
 
 
@@ -220,8 +221,8 @@ def _fetch_crypto_crc(code: str) -> float | None:
         price = data.get(coin_id, {}).get("crc")
         if price:
             return float(price)
-    except Exception:
-        pass
+    except Exception as e:
+        logger.warning("CoinGecko %s/CRC fetch failed: %s", code, e)
     return None
 
 

backend/tests/test_agent_tools.py

@@ -68,7 +68,7 @@ def make_receipt(period: str) -> MunicipalReceipt:
 
 
 def test_unbound_session_raises(session):
-    with pytest.raises(LookupError):
+    with pytest.raises(RuntimeError, match="not bound to agent context"):
         tools.get_accounts()