diff --git a/CHANGELOG.md b/CHANGELOG.md
new file mode 100644
index 0000000..46b035b
--- /dev/null
+++ b/CHANGELOG.md
@@ -0,0 +1,20 @@
+# Changelog
+
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [Unreleased]
+
+Unreleased changes will be displayed here upon implementation.
+
+## [0.2.0] - 2025-08-13
+
+### Added
+
+- [JSV](https://hexdocs.pm/jsv/JSV.html)-compatible JsonSchema definitions for `format` and `defaults` as
+  `ValueFormatter.Schema.Format` and `ValueFormatter.Schema.DefaultFormats`, respectively.
+
+[unreleased]: https://github.com/box-id/value_formatters/compare/0.2.0...HEAD
+[0.2.0]: https://github.com/box-id/value_formatters/releases/tag/0.2.0
\ No newline at end of file
diff --git a/lib/schemas.ex b/lib/schemas.ex
new file mode 100644
index 0000000..b1e5183
--- /dev/null
+++ b/lib/schemas.ex
@@ -0,0 +1,281 @@
+defmodule ValueFormatters.Schemas do
+  def number_options do
+    %{
+      precision: %{
+        type: :number,
+        description: "Number of decimal places"
+      },
+      unit: %{
+        type: :string,
+        description: "If set, the formatter appends ' ' + unit to the display value"
+      }
+    }
+  end
+
+  def date_options do
+    %{
+      date_display: %{
+        type: :string,
+        description: """
+        How the formatter should display the date portion:
+
+        - `full`: Wednesday, November 29, 2023
+
+        - `long`: November 29, 2023
+
+        - `medium`: Nov 29, 2023
+
+        - `short`: 11/29/23
+
+        - `none`: Don't display date
+        """,
+        enum: ["full", "long", "medium", "short", "none"],
+        default: "medium"
+      },
+      time_display: %{
+        type: :string,
+        description: """
+        How the formatter should display the time portion:
+
+        - `full`: 3:44:28 PM GMT
+
+        - `long`: 3:44:28 PM UTC
+
+        - `medium`: 3:44:28 PM
+
+        - `short`: 3:44 PM
+
+        - `none`: Don't display time
+        """,
+        enum: ["full", "long", "medium", "short", "none"],
+        default: "medium"
+      }
+    }
+  end
+
+  def date_unix_options do
+    %{
+      milliseconds: %{
+        type: :boolean,
+        default: false,
+        description:
+          "Whether the formatter should output the values milliseconds (instead of seconds)."
+      }
+    }
+  end
+
+  def coordinates_options do
+    %{
+      radius_display: %{
+        type: :boolean,
+        default: true,
+        description:
+          "Whether the formatter should include the radius/accuracy information (if present)."
+      }
+    }
+  end
+end
+
+defmodule ValueFormatters.Schemas.Format do
+  import ValueFormatters.Schemas
+
+  def json_schema() do
+    %{
+      description: "Formats for value formatting",
+      oneOf: [
+        %{
+          const: nil,
+          description: "Skip formatting and return raw value."
+        },
+        %{
+          type: :string,
+          title: "shorthand",
+          description: "A shorthand representation of the format",
+          enum: [
+            "number",
+            "string",
+            "date",
+            "date_relative",
+            "date_iso",
+            "date_unix",
+            "coordinates"
+          ]
+        },
+        %{
+          type: :object,
+          title: "string",
+          properties: %{
+            format: %{
+              const: "string",
+              description:
+                "Use to explicitly disable any kind of formatting that would otherwise take place, but still return a string."
+            }
+          },
+          required: [:format],
+          additionalProperties: false
+        },
+        %{
+          type: :object,
+          title: "number",
+          properties:
+            Map.merge(
+              %{
+                format: %{
+                  const: "number",
+                  description:
+                    "Use to display numeric values and format them according to the user's locale."
+                }
+              },
+              number_options()
+            ),
+          required: [:format],
+          additionalProperties: false
+        },
+        %{
+          type: :object,
+          title: "date",
+          properties:
+            Map.merge(
+              %{
+                format: %{
+                  const: "date",
+                  description:
+                    "Use to display date-time values and format them according to the user's locale."
+                }
+              },
+              date_options()
+            ),
+          required: [:format],
+          additionalProperties: false
+        },
+        %{
+          type: :object,
+          title: "date_relative",
+          properties: %{
+            format: %{
+              const: "date_relative",
+              description: """
+              Use format: "date_relative" to display a relative date string (e.g. “2 days ago”) by comparing the given value against the current date & time. Only the largest sensible unit is displayed, e.g. the formatter will only display “days” even when other components such as hours, minutes etc. aren't equal to zero.
+
+              The implementation can choose to update the displayed value in appropriate intervals. Also, it can choose to display the absolute date on user interaction, e.g. in a tooltip.
+
+              This format currently doesn't support any options.
+              """
+            }
+          },
+          required: [:format],
+          additionalProperties: false
+        },
+        %{
+          type: :object,
+          title: "date_iso",
+          properties: %{
+            format: %{
+              const: "date_iso",
+              description: "Use to display date-time values in ISO 8601 extended format."
+            }
+          },
+          required: [:format],
+          additionalProperties: false
+        },
+        %{
+          type: :object,
+          title: "date_unix",
+          properties:
+            Map.merge(
+              %{
+                format: %{
+                  const: "date_unix",
+                  description: "Use to display date-time values in seconds since unix epoch."
+                }
+              },
+              date_unix_options()
+            ),
+          required: [:format],
+          additionalProperties: false
+        },
+        %{
+          type: :object,
+          title: "coordinates",
+          properties:
+            Map.merge(
+              %{
+                format: %{
+                  const: "coordinates",
+                  description: "Use to display latitude & longitude information."
+                }
+              },
+              coordinates_options()
+            ),
+          required: [:format],
+          additionalProperties: false
+        }
+      ]
+    }
+  end
+end
+
+defmodule ValueFormatters.Schemas.DefaultFormats do
+  import ValueFormatters.Schemas
+
+  def json_schema() do
+    %{
+      type: :object,
+      description: "Default formats for value formatting",
+      properties: %{
+        number: %{
+          type: [:object, :null],
+          description:
+            "Use to display numeric values and format them according to the user's locale.",
+          properties: number_options(),
+          additionalProperties: false
+        },
+        string: %{
+          type: [:object, :null],
+          description:
+            "Use to explicitly disable any kind of formatting that would otherwise take place.",
+          properties: %{},
+          additionalProperties: false
+        },
+        date: %{
+          type: [:object, :null],
+          description:
+            "Use to to display date-time values and format them according to the user's locale.",
+          properties: date_options(),
+          additionalProperties: false
+        },
+        date_relative: %{
+          type: [:object, :null],
+          description: """
+          Use format: "date_relative" to display a relative date string (e.g. “2 days ago”) by comparing the given value against the current date & time. Only the largest sensible unit is displayed, e.g. the formatter will only display “days” even when other components such as hours, minutes etc. aren't equal to zero.
+
+          The implementation can choose to update the displayed value in appropriate intervals. Also, it can choose to display the absolute date on user interaction, e.g. in a tooltip.
+
+          This format currently doesn't support any options.
+          """,
+          properties: %{},
+          additionalProperties: false
+        },
+        date_iso: %{
+          type: [:object, :null],
+          description: "Use to display date-time values in ISO 8601 extended format.",
+          properties: %{},
+          additionalProperties: false
+        },
+        date_unix: %{
+          type: [:object, :null],
+          description: "Use to display date-time values in seconds since unix epoch.",
+          properties: date_unix_options(),
+          additionalProperties: false
+        },
+        coordinates: %{
+          type: [:object, :null],
+          description: "Use to display latitude & longitude information.",
+          properties: coordinates_options(),
+          additionalProperties: false
+        }
+      },
+      additionalProperties: false
+    }
+  end
+end
diff --git a/lib/value_formatters.ex b/lib/value_formatters.ex
index 35e4903..e9c0e96 100644
--- a/lib/value_formatters.ex
+++ b/lib/value_formatters.ex
@@ -195,7 +195,7 @@ defmodule ValueFormatters do
     value <> separator <> render_function.(unit)
   end
 
-  defp format_string(value, _string_definition), do: {:ok, value}
+  defp format_string(value, _string_definition), do: {:ok, to_string(value)}
 
   defp format_date(value, date_definition, opts) do
     with {:ok, value} <- pre_process_date_value(value, date_definition, opts) do
diff --git a/mix.exs b/mix.exs
index 8828d82..e12d6ef 100644
--- a/mix.exs
+++ b/mix.exs
@@ -4,7 +4,7 @@ defmodule ValueFormatters.MixProject do
   def project do
     [
       app: :value_formatters,
-      version: "0.1.3",
+      version: "0.2.0",
       elixir: "~> 1.15",
       elixirc_paths: elixirc_paths(Mix.env()),
       start_permanent: Mix.env() == :prod,
@@ -32,7 +32,8 @@ defmodule ValueFormatters.MixProject do
       {:mox, "~> 1.0", only: [:dev, :test]},
       {:timex, "~> 3.7", only: :test},
       {:ok, "~> 2.3.0"},
-      {:mix_test_watch, "~> 1.3", only: [:dev, :test]}
+      {:mix_test_watch, "~> 1.3", only: [:dev, :test]},
+      {:jsv, "~> 0.10", optional: true}
     ]
   end
 
diff --git a/mix.lock b/mix.lock
index fb176b9..3b19b74 100644
--- a/mix.lock
+++ b/mix.lock
@@ -19,6 +19,7 @@
   "hackney": {:hex, :hackney, "1.24.1", "f5205a125bba6ed4587f9db3cc7c729d11316fa8f215d3e57ed1c067a9703fa9", [:rebar3], [{:certifi, "~> 2.15.0", [hex: :certifi, repo: "hexpm", optional: false]}, {:idna, "~> 6.1.0", [hex: :idna, repo: "hexpm", optional: false]}, {:metrics, "~> 1.0.0", [hex: :metrics, repo: "hexpm", optional: false]}, {:mimerl, "~> 1.4", [hex: :mimerl, repo: "hexpm", optional: false]}, {:parse_trans, "3.4.1", [hex: :parse_trans, repo: "hexpm", optional: false]}, {:ssl_verify_fun, "~> 1.1.0", [hex: :ssl_verify_fun, repo: "hexpm", optional: false]}, {:unicode_util_compat, "~> 0.7.0", [hex: :unicode_util_compat, repo: "hexpm", optional: false]}], "hexpm", "f4a7392a0b53d8bbc3eb855bdcc919cd677358e65b2afd3840b5b3690c4c8a39"},
   "idna": {:hex, :idna, "6.1.1", "8a63070e9f7d0c62eb9d9fcb360a7de382448200fbbd1b106cc96d3d8099df8d", [:rebar3], [{:unicode_util_compat, "~> 0.7.0", [hex: :unicode_util_compat, repo: "hexpm", optional: false]}], "hexpm", "92376eb7894412ed19ac475e4a86f7b413c1b9fbb5bd16dccd57934157944cea"},
   "jason": {:hex, :jason, "1.4.4", "b9226785a9aa77b6857ca22832cffa5d5011a667207eb2a0ad56adb5db443b8a", [:mix], [{:decimal, "~> 1.0 or ~> 2.0", [hex: :decimal, repo: "hexpm", optional: true]}], "hexpm", "c5eb0cab91f094599f94d55bc63409236a8ec69a21a67814529e8d5f6cc90b3b"},
+  "jsv": {:hex, :jsv, "0.10.1", "a55790331196b92a17034f56cef48438dc407e6dca8cc570eff779f83f8680ea", [:mix], [{:abnf_parsec, "~> 2.0", [hex: :abnf_parsec, repo: "hexpm", optional: true]}, {:decimal, "~> 2.0", [hex: :decimal, repo: "hexpm", optional: true]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: true]}, {:nimble_options, "~> 1.0", [hex: :nimble_options, repo: "hexpm", optional: false]}, {:poison, "~> 5.0 or ~> 6.0", [hex: :poison, repo: "hexpm", optional: true]}], "hexpm", "2b51d3e90d7cdc839516c0c3ba0da21814f4666dbb94bcdf103def8766e78d74"},
   "makeup": {:hex, :makeup, "1.2.1", "e90ac1c65589ef354378def3ba19d401e739ee7ee06fb47f94c687016e3713d1", [:mix], [{:nimble_parsec, "~> 1.4", [hex: :nimble_parsec, repo: "hexpm", optional: false]}], "hexpm", "d36484867b0bae0fea568d10131197a4c2e47056a6fbe84922bf6ba71c8d17ce"},
   "makeup_elixir": {:hex, :makeup_elixir, "1.0.1", "e928a4f984e795e41e3abd27bfc09f51db16ab8ba1aebdba2b3a575437efafc2", [:mix], [{:makeup, "~> 1.0", [hex: :makeup, repo: "hexpm", optional: false]}, {:nimble_parsec, "~> 1.2.3 or ~> 1.3", [hex: :nimble_parsec, repo: "hexpm", optional: false]}], "hexpm", "7284900d412a3e5cfd97fdaed4f5ed389b8f2b4cb49efc0eb3bd10e2febf9507"},
   "makeup_erlang": {:hex, :makeup_erlang, "1.0.2", "03e1804074b3aa64d5fad7aa64601ed0fb395337b982d9bcf04029d68d51b6a7", [:mix], [{:makeup, "~> 1.0", [hex: :makeup, repo: "hexpm", optional: false]}], "hexpm", "af33ff7ef368d5893e4a267933e7744e46ce3cf1f61e2dccf53a111ed3aa3727"},
@@ -26,6 +27,7 @@
   "mimerl": {:hex, :mimerl, "1.4.0", "3882a5ca67fbbe7117ba8947f27643557adec38fa2307490c4c4207624cb213b", [:rebar3], [], "hexpm", "13af15f9f68c65884ecca3a3891d50a7b57d82152792f3e19d88650aa126b144"},
   "mix_test_watch": {:hex, :mix_test_watch, "1.3.0", "2ffc9f72b0d1f4ecf0ce97b044e0e3c607c3b4dc21d6228365e8bc7c2856dc77", [:mix], [{:file_system, "~> 0.2 or ~> 1.0", [hex: :file_system, repo: "hexpm", optional: false]}], "hexpm", "f9e5edca976857ffac78632e635750d158df14ee2d6185a15013844af7570ffe"},
   "mox": {:hex, :mox, "1.2.0", "a2cd96b4b80a3883e3100a221e8adc1b98e4c3a332a8fc434c39526babafd5b3", [:mix], [{:nimble_ownership, "~> 1.0", [hex: :nimble_ownership, repo: "hexpm", optional: false]}], "hexpm", "c7b92b3cc69ee24a7eeeaf944cd7be22013c52fcb580c1f33f50845ec821089a"},
+  "nimble_options": {:hex, :nimble_options, "1.1.1", "e3a492d54d85fc3fd7c5baf411d9d2852922f66e69476317787a7b2bb000a61b", [:mix], [], "hexpm", "821b2470ca9442c4b6984882fe9bb0389371b8ddec4d45a9504f00a66f650b44"},
   "nimble_ownership": {:hex, :nimble_ownership, "1.0.1", "f69fae0cdd451b1614364013544e66e4f5d25f36a2056a9698b793305c5aa3a6", [:mix], [], "hexpm", "3825e461025464f519f3f3e4a1f9b68c47dc151369611629ad08b636b73bb22d"},
   "nimble_parsec": {:hex, :nimble_parsec, "1.4.2", "8efba0122db06df95bfaa78f791344a89352ba04baedd3849593bfce4d0dc1c6", [:mix], [], "hexpm", "4b21398942dda052b403bbe1da991ccd03a053668d147d53fb8c4e0efe09c973"},
   "ok": {:hex, :ok, "2.3.0", "0a3d513ec9038504dc5359d44e14fc14ef59179e625563a1a144199cdc3a6d30", [:mix], [], "hexpm", "f0347b3f8f115bf347c704184b33cf084f2943771273f2b98a3707a5fa43c4d5"},
diff --git a/test/schemas_test.exs b/test/schemas_test.exs
new file mode 100644
index 0000000..fc9fccd
--- /dev/null
+++ b/test/schemas_test.exs
@@ -0,0 +1,160 @@
+defmodule ValueFormatters.SchemasTest do
+  use ExUnit.Case, async: true
+
+  alias ValueFormatters.Schemas.{
+    Format,
+    DefaultFormats
+  }
+
+  describe "Format Schema" do
+    test "accepts shorthands" do
+      assert {:ok, _} = validate_format("date")
+      assert {:ok, _} = validate_format("number")
+      assert {:ok, _} = validate_format("string")
+      assert {:ok, _} = validate_format("date_relative")
+      assert {:ok, _} = validate_format("date_unix")
+      assert {:ok, _} = validate_format("date_iso")
+      assert {:ok, _} = validate_format("coordinates")
+    end
+
+    test "accepts null shorthand" do
+      assert {:ok, _} = validate_format(nil)
+    end
+
+    test "accepts extended format" do
+      assert {:ok, _} = validate_format(%{"format" => "date"})
+    end
+
+    test "accepts date options" do
+      assert {:ok, _} =
+               validate_format(%{
+                 "format" => "date",
+                 "time_display" => "short",
+                 "date_display" => "long"
+               })
+    end
+
+    test "accepts number options" do
+      assert {:ok, _} =
+               validate_format(%{
+                 "format" => "number",
+                 "precision" => 3,
+                 "unit" => "°C"
+               })
+    end
+
+    test "accepts date_unix options" do
+      assert {:ok, _} =
+               validate_format(%{
+                 "format" => "date_unix",
+                 "milliseconds" => true
+               })
+    end
+
+    test "accepts coordinates options" do
+      assert {:ok, _} =
+               validate_format(%{
+                 "format" => "coordinates",
+                 "radius_display" => true
+               })
+    end
+
+    test "doesn't accept invalid format type" do
+      assert {:error, _} =
+               validate_default_formats(%{
+                 "format" => "foo"
+               })
+    end
+
+    test "doesn't accept invalid date options" do
+      assert {:error, _} =
+               validate_format(%{
+                 "format" => "date",
+                 "time_display" => "short",
+                 "date_display" => "long",
+                 "foo" => "bar"
+               })
+    end
+  end
+
+  describe "DefaultFormats Schema" do
+    test "accepts empty object" do
+      assert {:ok, _} = validate_default_formats(%{})
+    end
+
+    test "accepts null value" do
+      assert {:ok, _} = validate_default_formats(%{"number" => nil})
+    end
+
+    test "accepts number defaults" do
+      assert {:ok, _} =
+               validate_default_formats(%{
+                 "number" => %{
+                   "precision" => 2,
+                   "unit" => "kg"
+                 }
+               })
+    end
+
+    test "accepts date_unix defaults" do
+      assert {:ok, _} =
+               validate_default_formats(%{
+                 "date_unix" => %{
+                   "milliseconds" => true
+                 }
+               })
+    end
+
+    test "accepts date defaults" do
+      assert {:ok, _} =
+               validate_default_formats(%{
+                 "date" => %{
+                   "date_display" => "long",
+                   "time_display" => "short"
+                 }
+               })
+    end
+
+    test "accepts coordinate defaults" do
+      assert {:ok, _} =
+               validate_default_formats(%{
+                 "coordinates" => %{
+                   "radius_display" => false
+                 }
+               })
+    end
+
+    test "doesn't accept invalid date options" do
+      assert {:error, _} =
+               validate_default_formats(%{
+                 "date" => %{
+                   "date_display" => "long",
+                   "time_display" => "short",
+                   "foo" => "bar"
+                 }
+               })
+    end
+
+    test "doesn't accept invalid format type" do
+      assert {:error, _} =
+               validate_default_formats(%{
+                 "foo" => %{
+                   "date_display" => "long",
+                   "time_display" => "short"
+                 }
+               })
+    end
+  end
+
+  defp validate_format(format) do
+    format_schema = JSV.build!(Format)
+
+    JSV.validate(format, format_schema)
+  end
+
+  defp validate_default_formats(default_formats) do
+    default_formats_schema = JSV.build!(DefaultFormats)
+
+    JSV.validate(default_formats, default_formats_schema)
+  end
+end