Add resource Link (#974)

tests/issues/test_88_random_error.py

@@ -11,7 +11,7 @@ from anyio.abc import TaskStatus
 from mcp.client.session import ClientSession
 from mcp.server.lowlevel import Server
 from mcp.shared.exceptions import McpError
-from mcp.types import Content, TextContent
+from mcp.types import ContentBlock, TextContent
 
 
 @pytest.mark.anyio
@@ -31,7 +31,7 @@ async def test_notification_validation_error(tmp_path: Path):
     slow_request_complete = anyio.Event()
 
     @server.call_tool()
-    async def slow_tool(name: str, arg) -> Sequence[Content]:
+    async def slow_tool(name: str, arg) -> Sequence[ContentBlock]:
         nonlocal request_count
         request_count += 1
 

tests/server/fastmcp/test_integration.py

@@ -38,6 +38,7 @@ from mcp.types import (
     ProgressNotification,
     PromptReference,
     ReadResourceResult,
+    ResourceLink,
     ResourceListChangedNotification,
     ResourceTemplateReference,
     SamplingMessage,
@@ -152,6 +153,25 @@ def make_everything_fastmcp() -> FastMCP:
     def echo(message: str) -> str:
         return f"Echo: {message}"
 
+    # Tool that returns ResourceLinks
+    @mcp.tool(description="Lists files and returns resource links", title="List Files Tool")
+    def list_files() -> list[ResourceLink]:
+        """Returns a list of resource links for files matching the pattern."""
+
+        # Mock some file resources for testing
+        file_resources = [
+            {
+                "type": "resource_link",
+                "uri": "file:///project/README.md",
+                "name": "README.md",
+                "mimeType": "text/markdown",
+            }
+        ]
+
+        result: list[ResourceLink] = [ResourceLink.model_validate(file_json) for file_json in file_resources]
+
+        return result
+
     # Tool with sampling capability
     @mcp.tool(description="A tool that uses sampling to generate content", title="Sampling Tool")
     async def sampling_tool(prompt: str, ctx: Context) -> str:
@@ -762,7 +782,17 @@ async def call_all_mcp_features(session: ClientSession, collector: NotificationC
     assert isinstance(tool_result.content[0], TextContent)
     assert tool_result.content[0].text == "Echo: hello"
 
-    # 2. Tool with context (logging and progress)
+    # 2. Test tool that returns ResourceLinks
+    list_files_result = await session.call_tool("list_files")
+    assert len(list_files_result.content) == 1
+
+    # Rest should be ResourceLinks
+    content = list_files_result.content[0]
+    assert isinstance(content, ResourceLink)
+    assert str(content.uri).startswith("file:///")
+    assert content.name is not None
+    assert content.mimeType is not None
+
     # Test progress callback functionality
     progress_updates = []
 

tests/server/fastmcp/test_server.py

@@ -18,7 +18,7 @@ from mcp.shared.memory import (
 from mcp.types import (
     AudioContent,
     BlobResourceContents,
-    Content,
+    ContentBlock,
     EmbeddedResource,
     ImageContent,
     TextContent,
@@ -194,7 +194,7 @@ def image_tool_fn(path: str) -> Image:
     return Image(path)
 
 
-def mixed_content_tool_fn() -> list[Content]:
+def mixed_content_tool_fn() -> list[ContentBlock]:
     return [
         TextContent(type="text", text="Hello"),
         ImageContent(type="image", data="abc", mimeType="image/png"),