diff --git a/message_ix_models/tools/costs/config.py b/message_ix_models/tools/costs/config.py
index 91e33781c1..47eb0d9f4d 100644
--- a/message_ix_models/tools/costs/config.py
+++ b/message_ix_models/tools/costs/config.py
@@ -1,3 +1,6 @@
+from dataclasses import dataclass
+from typing import Literal, Optional
+
 BASE_YEAR = 2021
 ADJ_BASE_YEAR = 2020
 FIRST_MODEL_YEAR = 2020
@@ -11,3 +14,53 @@
 # Conversion rate from 2021 USD to 2005 USD
 # Taken from https://www.officialdata.org/us/inflation/2021?endYear=2005&amount=1
 CONVERSION_2021_TO_2005_USD = 0.72
+
+
+@dataclass
+class Config:
+    """Configuration for :mod:`.costs`."""
+
+    #: Base year for projections.
+    base_year: int = BASE_YEAR
+
+    #: Year of convergence; used when :attr:`.method` is "convergence". See
+    #: :func:`.create_projections_converge`.
+    convergence_year: int = 2050
+
+    #: Rate of increase/decrease of fixed operating and maintenance costs.
+    fom_rate: float = 0.025
+
+    #: Format of output. One of:
+    #:
+    #: - "iamc": IAMC time series data structure.
+    #: - "message": :mod:`message_ix` parameter data.
+    format: Literal["iamc", "message"] = "message"
+
+    #: Spatial resolution
+    node: Literal["R11", "R12", "R20"] = "R12"
+
+    #: Projection method; one of:
+    #:
+    #: - "convergence": uses :func:`.create_projections_converge`
+    #: - "gdp": :func:`.create_projections_gdp`
+    #: - "learning": :func:`.create_projections_converge`
+    method: Literal["convergence", "gdp", "learning"] = "gdp"
+
+    #: Model variant to prepare data for.
+    module: Literal["base", "materials"] = "base"
+
+    #: Reference region; default "{node}_NAM".
+    ref_region: Optional[str] = None
+
+    #: Set of SSPs referenced by :attr:`scenario`. One of:
+    #:
+    #: - "original": :obj:`SSP_2017`
+    #: - "updated": :obj:`SSP_2024`
+    scenario_version: Literal["original", "updated"] = "updated"
+
+    #: Scenario(s) for which to create data.
+    scenario: Literal["all", "LED", "SSP1", "SSP2", "SSP3", "SSP4", "SSP5"] = "all"
+
+    def __post_init__(self):
+        if self.ref_region is None:
+            self.ref_region = f"{self.node}_NAM"
diff --git a/message_ix_models/util/config.py b/message_ix_models/util/config.py
index 0c48fe467c..8b45ab641e 100644
--- a/message_ix_models/util/config.py
+++ b/message_ix_models/util/config.py
@@ -97,7 +97,9 @@ def read_file(self, path: Path, fail="raise") -> None:
                     # Use name manipulation on the attribute value also
                     value = existing.replace(**value)
                 elif not isinstance(existing, type):
-                    value = replace(existing, **value)
+                    # https://github.com/python/mypy/issues/15843
+                    # TODO Check that fix is available in mypy 1.7.x; remove
+                    value = replace(existing, **value)  # type: ignore [misc]
             setattr(self, key, value)
 
     def replace(self, **kwargs):