feat: add UriTemplate.is_template() static method

Cheap heuristic for distinguishing concrete URIs from templates
without full parsing. Returns True if the string contains at least
one {...} pair. Does not validate; a True result does not guarantee
parse() will succeed.

Matches the TypeScript SDK's UriTemplate.isTemplate() utility.

Author: maxisbey

src/mcp/shared/uri_template.py

@@ -210,6 +210,28 @@ class UriTemplate:
     _variables: tuple[Variable, ...] = field(repr=False, compare=False)
     _pattern: re.Pattern[str] = field(repr=False, compare=False)
 
+    @staticmethod
+    def is_template(value: str) -> bool:
+        """Check whether a string contains URI template expressions.
+
+        A cheap heuristic for distinguishing concrete URIs from templates
+        without the cost of full parsing. Returns ``True`` if the string
+        contains at least one ``{...}`` pair.
+
+        Example::
+
+            >>> UriTemplate.is_template("file://docs/{name}")
+            True
+            >>> UriTemplate.is_template("file://docs/readme.txt")
+            False
+
+        Note:
+            This does not validate the template. A ``True`` result does
+            not guarantee :meth:`parse` will succeed.
+        """
+        open_i = value.find("{")
+        return open_i != -1 and value.find("}", open_i) != -1
+
     @classmethod
     def parse(
         cls,

tests/shared/test_uri_template.py

@@ -12,6 +12,24 @@ def test_parse_literal_only():
     assert str(tmpl) == "file://docs/readme.txt"
 
 
+@pytest.mark.parametrize(
+    ("value", "expected"),
+    [
+        ("file://docs/{name}", True),
+        ("file://docs/readme.txt", False),
+        ("", False),
+        ("{a}", True),
+        ("{", False),
+        ("}", False),
+        ("}{", False),
+        ("prefix{+path}/suffix", True),
+        ("{invalid syntax but still a template}", True),
+    ],
+)
+def test_is_template(value: str, expected: bool):
+    assert UriTemplate.is_template(value) is expected
+
+
 def test_parse_simple_variable():
     tmpl = UriTemplate.parse("file://docs/{name}")
     assert tmpl.variables == (Variable(name="name", operator=""),)