diff --git a/docs/tool-guide.md b/docs/tool-guide.md
index ed54a58..5912597 100644
--- a/docs/tool-guide.md
+++ b/docs/tool-guide.md
@@ -40,10 +40,13 @@ Header cells that are empty or whitespace-only are reported by zero-based positi
 `empty_header_indices`; a blank name is a warning, not an invalid document, and the
 original names are kept in `columns` unchanged.
 
-## hash_text(text, algorithm="sha256")
+## hash_text(text, algorithm="sha256", uppercase=False)
 
 Algorithms: `sha256`, `sha512`, `blake2b`. Returns `algorithm` and lowercase
-hexadecimal `digest`. Text is encoded as UTF-8. Empty strings are supported.
+hexadecimal `digest`. Pass `uppercase=True` for an uppercase digest; the
+`algorithm` name is unchanged either way. For example,
+`hash_text("abc", uppercase=True)` starts with `BA7816BF`. Text is encoded as
+UTF-8. Empty strings are supported.
 These hashes compare content; this tool does not provide password storage.
 Unknown algorithms raise `ValueError`.
 
diff --git a/src/mcp_tools_lab/tools/hashing.py b/src/mcp_tools_lab/tools/hashing.py
index e66e761..44161d3 100644
--- a/src/mcp_tools_lab/tools/hashing.py
+++ b/src/mcp_tools_lab/tools/hashing.py
@@ -4,9 +4,14 @@
 from typing import Literal
 
 
-def hash_text(text: str, algorithm: Literal["sha256", "sha512", "blake2b"] = "sha256") -> dict:
-    """Hash UTF-8 text using SHA-256, SHA-512, or BLAKE2b; return lowercase hex."""
+def hash_text(text: str, algorithm: Literal["sha256", "sha512", "blake2b"] = "sha256", uppercase: bool = False) -> dict:
+    """Hash UTF-8 text using SHA-256, SHA-512, or BLAKE2b; return hex.
+
+    The digest is lowercase by default. Pass uppercase=True for an uppercase
+    digest; the algorithm name is returned unchanged.
+    """
     algorithms = {"sha256": hashlib.sha256, "sha512": hashlib.sha512, "blake2b": hashlib.blake2b}
     if algorithm not in algorithms:
         raise ValueError("algorithm must be sha256, sha512, or blake2b.")
-    return {"algorithm": algorithm, "digest": algorithms[algorithm](text.encode("utf-8")).hexdigest()}
+    digest = algorithms[algorithm](text.encode("utf-8")).hexdigest()
+    return {"algorithm": algorithm, "digest": digest.upper() if uppercase else digest}
diff --git a/tests/test_hashing.py b/tests/test_hashing.py
index e8e8be4..4e8e6b2 100644
--- a/tests/test_hashing.py
+++ b/tests/test_hashing.py
@@ -16,3 +16,29 @@ def test_algorithms(algorithm, length):
 def test_unsupported_algorithm():
     with pytest.raises(ValueError, match="algorithm"):
         hash_text("abc", "md5")
+
+
+def test_uppercase_digest():
+    result = hash_text("abc", uppercase=True)
+    assert result["digest"] == "BA7816BF8F01CFEA414140DE5DAE2223B00361A396177A9CB410FF61F20015AD"
+    assert result["algorithm"] == "sha256"
+
+
+def test_uppercase_is_optional_and_algorithm_is_unchanged():
+    assert hash_text("abc")["digest"].startswith("ba7816bf")
+    assert hash_text("abc", uppercase=False) == hash_text("abc")
+
+
+@pytest.mark.parametrize("algorithm", ["sha256", "sha512", "blake2b"])
+def test_uppercase_supports_every_algorithm(algorithm):
+    lower = hash_text("abc", algorithm)
+    upper = hash_text("abc", algorithm, uppercase=True)
+    assert upper["algorithm"] == algorithm
+    assert upper["digest"] == lower["digest"].upper()
+    assert len(upper["digest"]) == len(lower["digest"])
+
+
+def test_uppercase_empty_text():
+    result = hash_text("", uppercase=True)
+    assert result["digest"] == hash_text("", "sha256")["digest"].upper()
+    assert result["digest"] == "E3B0C44298FC1C149AFBF4C8996FB92427AE41E4649B934CA495991B7852B855"