diff --git a/src/coretrace_python/engine.py b/src/coretrace_python/engine.py
index e29a52c..63830e7 100644
--- a/src/coretrace_python/engine.py
+++ b/src/coretrace_python/engine.py
@@ -176,13 +176,14 @@
 )
 
 
-def rule_descriptions(registry: PluginRegistry) -> Mapping[str, RuleDescription]:
+def rule_descriptions(plugins: Iterable[Plugin]) -> Mapping[str, RuleDescription]:
     """What every rule of a check detects, for its report: the rules the engine reports
-    itself, and those each loaded plugin describes, the first declaration of an id kept."""
+    itself, and those each of its plugins describes, loaded or given as an instance, the
+    first declaration of an id kept."""
 
     described: dict[str, RuleDescription] = dict(ENGINE_RULES)
-    for loaded in registry:
-        for rule_id, description in loaded.plugin.rules.items():
+    for plugin in plugins:
+        for rule_id, description in plugin.rules.items():
             described.setdefault(rule_id, description)
     return MappingProxyType(described)
 
@@ -395,7 +396,7 @@ def analyze_file(source: SourceFile, plugin_roots: Sequence[Path], root: Path |
     functions = len(analyzable_functions(manager.module))
     coverage = Coverage((FileCoverage(str(source.source_id), "analysed", functions, len(supported)),))
     kept, suppressed = partition(findings, lambda sid: source.text if sid == source.source_id else None)
-    return FileAnalysis(kept, coverage, suppressed, rule_descriptions(registry))
+    return FileAnalysis(kept, coverage, suppressed, rule_descriptions(loaded.plugin for loaded in registry))
 
 
 def resolve_dependencies(root: Path, sources: SourceManager) -> DependencyGraph:
@@ -692,7 +693,7 @@ def analyze_project(
         suppressed,
         accepted,
         components,
-        rule_descriptions(registry),
+        rule_descriptions(all_plugins),
     )
 
 
diff --git a/tests/test_rule_descriptions_of_given_plugins.py b/tests/test_rule_descriptions_of_given_plugins.py
new file mode 100644
index 0000000..f39d5f9
--- /dev/null
+++ b/tests/test_rule_descriptions_of_given_plugins.py
@@ -0,0 +1,40 @@
+"""Acceptance tests for the review of #274: a plugin given to ``analyze_project`` as an
+instance, rather than loaded from a plugin root, describes its rules in the report as a
+loaded plugin does, the first declaration of an id kept.
+"""
+
+from __future__ import annotations
+
+from collections.abc import Mapping, Sequence
+from pathlib import Path
+from typing import ClassVar
+
+from coretrace_python import engine
+from coretrace_python.findings import Finding, RuleDescription
+from coretrace_python.plugins import Plugin, PluginContext
+
+QUIET = RuleDescription("Quiet rule", "A rule of a plugin given as an instance.")
+
+
+class Quiet(Plugin):
+    name: ClassVar[str] = "quiet"
+    rules: ClassVar[Mapping[str, RuleDescription]] = {
+        "quiet-rule": QUIET,
+        "command-injection": RuleDescription("Another title", "Another description."),
+    }
+
+    def analyze(self, ctx: PluginContext) -> Sequence[Finding]:
+        return ()
+
+
+def analysed(tmp_path: Path) -> engine.ProjectAnalysis:
+    (tmp_path / "app.py").write_text("x = 1\n", encoding="utf-8")
+    return engine.analyze_project(tmp_path, [engine.BUNDLED_PLUGINS], plugins=[Quiet()])
+
+
+def test_a_plugin_given_as_an_instance_describes_its_rules(tmp_path: Path) -> None:
+    assert analysed(tmp_path).rules["quiet-rule"] == QUIET
+
+
+def test_a_loaded_plugin_keeps_the_description_of_a_rule_an_instance_describes_too(tmp_path: Path) -> None:
+    assert analysed(tmp_path).rules["command-injection"].title == "Command injection"