diff --git a/python/CHANGES.md b/python/CHANGES.md
index a1ba62b..f8f4dc6 100644
--- a/python/CHANGES.md
+++ b/python/CHANGES.md
@@ -1,5 +1,10 @@
 # insta-science
 
+## 0.2.0
+
+Expose the `insta_science.ensure_installed` API for programmatic access
+to the `science` binary's path.
+
 ## 0.1.0
 
 Initial release.
diff --git a/python/RELEASE.md b/python/RELEASE.md
index 9e7d34d..77646e6 100644
--- a/python/RELEASE.md
+++ b/python/RELEASE.md
@@ -4,7 +4,7 @@
 
 ### Version Bump and Changelog
 
-1. Bump the version in [`insta_science/__init__.py`](insta_science/__init__.py).
+1. Bump the version in [`insta_science/version.py`](insta_science/version.py).
 2. Run `uv run dev-cmd` as a sanity check on the state of the project.
 3. Update [`CHANGES.md`](CHANGES.md) with any changes that are likely to be useful to consumers.
 4. Open a PR with these changes and land it on https://github.com/a-scie/science-installers main.
diff --git a/python/insta_science/__init__.py b/python/insta_science/__init__.py
index d3e0961..0da3e88 100644
--- a/python/insta_science/__init__.py
+++ b/python/insta_science/__init__.py
@@ -1,4 +1,24 @@
 # Copyright 2024 Science project contributors.
 # Licensed under the Apache License, Version 2.0 (see LICENSE).
 
-__version__ = "0.1.0"
+from ._internal import (
+    Digest,
+    Fingerprint,
+    InputError,
+    Platform,
+    Science,
+    ScienceNotFound,
+    ensure_installed,
+)
+from .version import __version__
+
+__all__ = (
+    "Digest",
+    "Fingerprint",
+    "InputError",
+    "Platform",
+    "Science",
+    "ScienceNotFound",
+    "__version__",
+    "ensure_installed",
+)
diff --git a/python/insta_science/__main__.py b/python/insta_science/__main__.py
index 84511bc..2eddf9f 100644
--- a/python/insta_science/__main__.py
+++ b/python/insta_science/__main__.py
@@ -1,7 +1,7 @@
 # Copyright 2024 Science project contributors.
 # Licensed under the Apache License, Version 2.0 (see LICENSE).
 
-from insta_science import shim
+from . import shim
 
 if __name__ == "__main__":
-    shim.science()
+    shim.main()
diff --git a/python/insta_science/_internal/__init__.py b/python/insta_science/_internal/__init__.py
new file mode 100644
index 0000000..3cd60fa
--- /dev/null
+++ b/python/insta_science/_internal/__init__.py
@@ -0,0 +1,18 @@
+# Copyright 2024 Science project contributors.
+# Licensed under the Apache License, Version 2.0 (see LICENSE).
+
+from .errors import InputError, ScienceNotFound
+from .hashing import Fingerprint
+from .model import Digest, Science
+from .platform import Platform
+from .science import ensure_installed
+
+__all__ = (
+    "Digest",
+    "Fingerprint",
+    "InputError",
+    "Platform",
+    "Science",
+    "ScienceNotFound",
+    "ensure_installed",
+)
diff --git a/python/insta_science/a_scie.py b/python/insta_science/_internal/a_scie.py
similarity index 89%
rename from python/insta_science/a_scie.py
rename to python/insta_science/_internal/a_scie.py
index c716208..37ac325 100644
--- a/python/insta_science/a_scie.py
+++ b/python/insta_science/_internal/a_scie.py
@@ -9,10 +9,10 @@
 
 from packaging.version import Version
 
-from insta_science.fetcher import fetch_and_verify
-from insta_science.hashing import Digest, Fingerprint
-from insta_science.model import Science, Url
-from insta_science.platform import Platform
+from .fetcher import fetch_and_verify
+from .hashing import Digest, Fingerprint
+from .model import Science, Url
+from .platform import Platform
 
 
 @dataclass(frozen=True)
diff --git a/python/insta_science/cache.py b/python/insta_science/_internal/cache.py
similarity index 100%
rename from python/insta_science/cache.py
rename to python/insta_science/_internal/cache.py
diff --git a/python/insta_science/errors.py b/python/insta_science/_internal/errors.py
similarity index 80%
rename from python/insta_science/errors.py
rename to python/insta_science/_internal/errors.py
index 55d161a..94ad651 100644
--- a/python/insta_science/errors.py
+++ b/python/insta_science/_internal/errors.py
@@ -16,3 +16,10 @@ class InputError(ValueError):
 
 class InvalidProjectError(InputError):
     """Indicates bad pyproject.toml configuration for `[tool.insta-science]`."""
+
+
+class ScienceNotFound(Exception):
+    """Indicates the science binary could not be found.
+
+    This generally means there was an error downloading a science binary.
+    """
diff --git a/python/insta_science/fetcher.py b/python/insta_science/_internal/fetcher.py
similarity index 93%
rename from python/insta_science/fetcher.py
rename to python/insta_science/_internal/fetcher.py
index 525cfcf..81fc3b4 100644
--- a/python/insta_science/fetcher.py
+++ b/python/insta_science/_internal/fetcher.py
@@ -14,11 +14,11 @@
 import httpx
 from tqdm import tqdm
 
-from insta_science import hashing
-from insta_science.cache import Missing, download_cache
-from insta_science.errors import InputError
-from insta_science.hashing import Digest, ExpectedDigest, Fingerprint
-from insta_science.model import Url
+from . import hashing
+from .cache import Missing, download_cache
+from .errors import InputError
+from .hashing import Digest, ExpectedDigest, Fingerprint
+from .model import Url
 
 logger = logging.getLogger(__name__)
 
@@ -83,7 +83,7 @@ def require_password(auth_type: str) -> str:
     return None
 
 
-def configured_client(url: Url, headers: Mapping[str, str] | None = None) -> httpx.Client:
+def _configured_client(url: Url, headers: Mapping[str, str] | None = None) -> httpx.Client:
     headers = dict(headers) if headers else {}
     auth = _configure_auth(url) if "Authorization" not in headers else None
     return httpx.Client(follow_redirects=True, headers=headers, auth=auth)
@@ -95,7 +95,7 @@ def _fetch_to_cache(
     with download_cache().get_or_create(url, ttl=ttl) as cache_result:
         if isinstance(cache_result, Missing):
             with (
-                configured_client(url, headers).stream("GET", url) as response,
+                _configured_client(url, headers).stream("GET", url) as response,
                 cache_result.work.open("wb") as cache_fp,
             ):
                 for data in response.iter_bytes():
@@ -115,7 +115,7 @@ def _maybe_expected_digest(
         return ExpectedDigest(fingerprint=fingerprint, algorithm=algorithm)
     elif isinstance(fingerprint, Url):
         url = fingerprint
-        with configured_client(url, headers) as client:
+        with _configured_client(url, headers) as client:
             return ExpectedDigest(
                 fingerprint=Fingerprint(client.get(url).text.split(" ", 1)[0].strip()),
                 algorithm=algorithm,
@@ -134,7 +134,7 @@ def _expected_digest(
     if expected_digest:
         return expected_digest
 
-    with configured_client(url, headers) as client:
+    with _configured_client(url, headers) as client:
         return ExpectedDigest(
             fingerprint=Fingerprint(client.get(f"{url}.{algorithm}").text.split(" ", 1)[0].strip()),
             algorithm=algorithm,
@@ -155,7 +155,7 @@ def fetch_and_verify(
             # TODO(John Sirois): XXX: Log or invoke callback for logging.
             # click.secho(f"Downloading {url} ...", fg="green")
             work = cache_result.work
-            with configured_client(url, headers) as client:
+            with _configured_client(url, headers) as client:
                 expected_digest = _expected_digest(
                     url, headers, fingerprint, algorithm=digest_algorithm
                 )
diff --git a/python/insta_science/hashing.py b/python/insta_science/_internal/hashing.py
similarity index 98%
rename from python/insta_science/hashing.py
rename to python/insta_science/_internal/hashing.py
index cdca240..05c4916 100644
--- a/python/insta_science/hashing.py
+++ b/python/insta_science/_internal/hashing.py
@@ -9,7 +9,7 @@
 from pathlib import Path
 from typing import Callable
 
-from insta_science.errors import InputError
+from .errors import InputError
 
 DEFAULT_ALGORITHM = "sha256"
 
diff --git a/python/insta_science/model.py b/python/insta_science/_internal/model.py
similarity index 92%
rename from python/insta_science/model.py
rename to python/insta_science/_internal/model.py
index efcab92..6a552ff 100644
--- a/python/insta_science/model.py
+++ b/python/insta_science/_internal/model.py
@@ -9,7 +9,7 @@
 
 from packaging.version import Version
 
-from insta_science.hashing import Digest
+from .hashing import Digest
 
 
 @dataclass(frozen=True)
diff --git a/python/insta_science/parser.py b/python/insta_science/_internal/parser.py
similarity index 94%
rename from python/insta_science/parser.py
rename to python/insta_science/_internal/parser.py
index 90d556d..0a904ed 100644
--- a/python/insta_science/parser.py
+++ b/python/insta_science/_internal/parser.py
@@ -7,10 +7,10 @@
 
 from packaging.version import InvalidVersion, Version
 
-from insta_science.errors import InputError
-from insta_science.hashing import Digest, Fingerprint
-from insta_science.model import Science
-from insta_science.project import PyProjectToml
+from .errors import InputError
+from .hashing import Digest, Fingerprint
+from .model import Science
+from .project import PyProjectToml
 
 
 def _assert_dict_str_keys(obj: Any, *, path: str) -> dict[str, Any]:
diff --git a/python/insta_science/platform.py b/python/insta_science/_internal/platform.py
similarity index 97%
rename from python/insta_science/platform.py
rename to python/insta_science/_internal/platform.py
index 79acd75..9e76578 100644
--- a/python/insta_science/platform.py
+++ b/python/insta_science/_internal/platform.py
@@ -7,7 +7,7 @@
 from enum import Enum
 from functools import cache
 
-from insta_science.errors import InputError
+from .errors import InputError
 
 
 class Platform(Enum):
diff --git a/python/insta_science/project.py b/python/insta_science/_internal/project.py
similarity index 97%
rename from python/insta_science/project.py
rename to python/insta_science/_internal/project.py
index ae0896a..0117606 100644
--- a/python/insta_science/project.py
+++ b/python/insta_science/_internal/project.py
@@ -10,7 +10,7 @@
 from pathlib import Path
 from typing import Any
 
-from insta_science.errors import InputError, InvalidProjectError
+from .errors import InputError, InvalidProjectError
 
 try:
     import tomllib as toml  # type: ignore[import-not-found]
diff --git a/python/insta_science/_internal/science.py b/python/insta_science/_internal/science.py
new file mode 100644
index 0000000..d29aa6f
--- /dev/null
+++ b/python/insta_science/_internal/science.py
@@ -0,0 +1,101 @@
+# Copyright 2024 Science project contributors.
+# Licensed under the Apache License, Version 2.0 (see LICENSE).
+
+from __future__ import annotations
+
+import shutil
+import subprocess
+import sys
+from datetime import timedelta
+from pathlib import Path, PurePath
+from subprocess import CalledProcessError
+
+import colors
+import httpx
+from packaging.version import Version
+
+from . import a_scie, parser, project
+from .cache import Missing, download_cache
+from .errors import InputError, ScienceNotFound
+from .hashing import ExpectedDigest
+from .model import Science
+from .platform import Platform
+
+
+def _find_science_on_path(science: Science) -> PurePath | None:
+    url = "file://<just-a-cache-key>/science"
+    ttl: timedelta | None = None
+    if science.version:
+        url = f"{url}/v{science.version}"
+        if science.digest:
+            url = f"{url}#{science.digest.fingerprint}:{science.digest.size}"
+    else:
+        ttl = timedelta(days=5)
+
+    with download_cache().get_or_create(url=url, ttl=ttl) as cache_result:
+        if isinstance(cache_result, Missing):
+            current_platform = Platform.current()
+            for binary_name in (
+                current_platform.binary_name("science"),
+                current_platform.binary_name("science-fat"),
+                current_platform.qualified_binary_name("science"),
+                current_platform.qualified_binary_name("science-fat"),
+            ):
+                science_exe = shutil.which(binary_name)
+                if not science_exe:
+                    continue
+                if science.version:
+                    if science.version != Version(
+                        subprocess.run(
+                            args=[science_exe, "-V"], text=True, stdout=subprocess.PIPE
+                        ).stdout.strip()
+                    ):
+                        continue
+                    if science.digest and science.digest.fingerprint:
+                        expected_digest = ExpectedDigest(
+                            fingerprint=science.digest.fingerprint, size=science.digest.size
+                        )
+                        try:
+                            expected_digest.check_path(Path(science_exe))
+                        except InputError:
+                            continue
+                shutil.copy(science_exe, cache_result.work)
+                return cache_result.path
+            return None
+    return cache_result.path
+
+
+def ensure_installed(spec: Science | None = None) -> PurePath:
+    """Ensures an appropriate science binary is installed and returns its path.
+
+    Args:
+        spec: An optional specification of which science binary is required.
+
+    Returns:
+        The path of a science binary meeting the supplied ``spec``, if any.
+
+    Raises:
+        InputError: No ``spec`` was supplied ; so the information about which ``science`` binary to
+            install was parsed from ``pyproject.toml`` and found to have errors.
+        ScienceNotFound: The science binary could not be found locally or downloaded.
+    """
+    if spec is not None:
+        science = spec
+    else:
+        try:
+            pyproject_toml = project.find_pyproject_toml()
+            science = parser.configured_science(pyproject_toml) if pyproject_toml else Science()
+        except InputError as e:
+            sys.exit(f"{colors.red('Configuration error')}: {colors.yellow(str(e))}")
+
+    try:
+        return _find_science_on_path(science) or a_scie.science(science)
+    except (
+        OSError,
+        CalledProcessError,
+        httpx.HTTPError,
+        httpx.InvalidURL,
+        httpx.CookieConflict,
+        httpx.StreamError,
+    ) as e:
+        raise ScienceNotFound(str(e))
diff --git a/python/insta_science/shim.py b/python/insta_science/shim.py
index 556e7c5..1e70f4b 100644
--- a/python/insta_science/shim.py
+++ b/python/insta_science/shim.py
@@ -4,95 +4,21 @@
 from __future__ import annotations
 
 import os
-import shutil
 import subprocess
 import sys
-from datetime import timedelta
-from pathlib import Path, PurePath
-from subprocess import CalledProcessError
 from typing import NoReturn
 
 import colors
-import httpx
-from packaging.version import Version
 
-from insta_science import a_scie, parser, project
-from insta_science.cache import Missing, download_cache
-from insta_science.errors import InputError
-from insta_science.hashing import ExpectedDigest
-from insta_science.model import Science
-from insta_science.platform import Platform
+from . import InputError, Platform, ScienceNotFound, ensure_installed
 
 
-def _find_science_on_path(science: Science) -> PurePath | None:
-    cache = download_cache()
-    url = f"file://{cache.base_dir}/science"
-    ttl: timedelta | None = None
-    if science.version:
-        url = f"{url}/v{science.version}"
-        if science.digest:
-            url = f"{url}#{science.digest.fingerprint}:{science.digest.size}"
-    else:
-        ttl = timedelta(days=5)
-
-    with cache.get_or_create(url=url, ttl=ttl) as cache_result:
-        if isinstance(cache_result, Missing):
-            current_platform = Platform.current()
-            for binary_name in (
-                current_platform.binary_name("science"),
-                current_platform.binary_name("science-fat"),
-                current_platform.qualified_binary_name("science"),
-                current_platform.qualified_binary_name("science-fat"),
-            ):
-                science_exe = shutil.which(binary_name)
-                if not science_exe:
-                    continue
-                if science.version:
-                    if science.version != Version(
-                        subprocess.run(
-                            args=[science_exe, "-V"], text=True, stdout=subprocess.PIPE
-                        ).stdout.strip()
-                    ):
-                        continue
-                    if science.digest and science.digest.fingerprint:
-                        expected_digest = ExpectedDigest(
-                            fingerprint=science.digest.fingerprint, size=science.digest.size
-                        )
-                        try:
-                            expected_digest.check_path(Path(science_exe))
-                        except InputError:
-                            continue
-                shutil.copy(science_exe, cache_result.work)
-                return cache_result.path
-            return None
-    return cache_result.path
-
-
-def science(spec: Science | None = None) -> NoReturn:
-    """Ensures an appropriate science binary is installed and then forwards to it.
-
-    spec: An optional specification of which science binary is required.
-    """
-    if spec is not None:
-        science = spec
-    else:
-        try:
-            pyproject_toml = project.find_pyproject_toml()
-            science = parser.configured_science(pyproject_toml) if pyproject_toml else Science()
-        except InputError as e:
-            sys.exit(f"{colors.red('Configuration error')}: {colors.yellow(str(e))}")
-
+def main() -> NoReturn:
     try:
-        science_exe = _find_science_on_path(science) or a_scie.science(science)
-    except (
-        OSError,
-        CalledProcessError,
-        InputError,
-        httpx.HTTPError,
-        httpx.InvalidURL,
-        httpx.CookieConflict,
-        httpx.StreamError,
-    ) as e:
+        science_exe = ensure_installed()
+    except InputError as e:
+        sys.exit(f"{colors.red('Configuration error')}: {colors.yellow(str(e))}")
+    except ScienceNotFound as e:
         sys.exit(colors.red(str(e)))
 
     argv = [str(science_exe), *sys.argv[1:]]
diff --git a/python/insta_science/version.py b/python/insta_science/version.py
new file mode 100644
index 0000000..a823ed7
--- /dev/null
+++ b/python/insta_science/version.py
@@ -0,0 +1,4 @@
+# Copyright 2024 Science project contributors.
+# Licensed under the Apache License, Version 2.0 (see LICENSE).
+
+__version__ = "0.2.0"
diff --git a/python/pyproject.toml b/python/pyproject.toml
index 9279b1e..866e92d 100644
--- a/python/pyproject.toml
+++ b/python/pyproject.toml
@@ -50,11 +50,11 @@ Repository = "https://github.com/a-scie/science-installers/tree/main/python"
 Changelog = "https://github.com/a-scie/science-installers/blob/main/python/CHANGES.md"
 
 [project.scripts]
-insta-science = "insta_science.shim:science"
+insta-science = "insta_science.shim:main"
 insta-science-util = "insta_science.util:main"
 
 [tool.setuptools.dynamic]
-version = {attr = "insta_science.__version__"}
+version = {attr = "insta_science.version.__version__"}
 
 [tool.setuptools.packages.find]
 where = ["."]
diff --git a/python/tests/test_shim.py b/python/tests/test_shim.py
index 15aad86..f042d44 100644
--- a/python/tests/test_shim.py
+++ b/python/tests/test_shim.py
@@ -9,7 +9,7 @@
 import pytest
 from packaging.version import Version
 
-from insta_science.platform import Platform
+from insta_science import Platform
 
 
 def test_self() -> None:
diff --git a/python/uv.lock b/python/uv.lock
index a3a539c..2e1e140 100644
--- a/python/uv.lock
+++ b/python/uv.lock
@@ -149,7 +149,7 @@ wheels = [
 
 [[package]]
 name = "insta-science"
-version = "0.1.0.dev0"
+version = "0.2.0"
 source = { editable = "." }
 dependencies = [
     { name = "ansicolors" },