diff --git a/planemo/linters/biocontainer_registered.py b/planemo/linters/biocontainer_registered.py
index 01ac56349..a96381d88 100644
--- a/planemo/linters/biocontainer_registered.py
+++ b/planemo/linters/biocontainer_registered.py
@@ -1,6 +1,7 @@
 """Ensure best-practice biocontainer registered for this tool."""
 
 from typing import (
+    List,
     Optional,
     TYPE_CHECKING,
 )
@@ -42,7 +43,7 @@ def lint(cls, tool_source: "ToolSource", lint_ctx: "LintContext"):
         name = mulled_container_name("biocontainers", targets)
         if not name:
             requirements_node = xml_node_from_toolsource(tool_source, "requirements")
-            lint_ctx.warn(MESSAGE_WARN_NO_CONTAINER, linter=cls.name(), node=requirements)
+            lint_ctx.warn(MESSAGE_WARN_NO_CONTAINER, linter=cls.name(), node=requirements_node)
 
 
 def mulled_container_name(namespace: str, targets: List[CondaTarget]) -> Optional[str]:
diff --git a/planemo/linters/conda_requirements.py b/planemo/linters/conda_requirements.py
index 3f13d7bd8..5836f7234 100644
--- a/planemo/linters/conda_requirements.py
+++ b/planemo/linters/conda_requirements.py
@@ -15,6 +15,7 @@
 )
 
 if TYPE_CHECKING:
+    from galaxy.tool_util.deps.conda_util import CondaTarget
     from galaxy.tool_util.lint import LintContext
     from galaxy.tool_util.parser.interface import ToolSource
 
@@ -32,7 +33,7 @@ def lint(cls, tool_source: "ToolSource", lint_ctx: "LintContext"):
             if best_hit and exact:
                 message = f"Requirement [{conda_target_str}] matches target in best practice Conda channel [{best_hit.get('channel')}]."
                 requirements_node = xml_node_from_toolsource(tool_source, "requirements")
-                lint_ctx.info(message, linter=cls.name(), node=requirements_nodes)
+                lint_ctx.info(message, linter=cls.name(), node=requirements_node)
 
 
 class CondaRequirementInexact(Linter):
@@ -63,7 +64,7 @@ def lint(cls, tool_source: "ToolSource", lint_ctx: "LintContext"):
                 lint_ctx.warn(message, linter=cls.name(), node=requirements_node)
 
 
-def _requirements_conda_targets(tool_source: "ToolSource") -> Generator[CondaTarget]:
+def _requirements_conda_targets(tool_source: "ToolSource") -> Generator["CondaTarget"]:
     requirements, *_ = tool_source.parse_requirements_and_containers()
     for requirement in requirements:
         conda_target = requirement_to_conda_targets(requirement)
diff --git a/planemo/shed_lint.py b/planemo/shed_lint.py
index 62d2ecdcc..2e63401f3 100644
--- a/planemo/shed_lint.py
+++ b/planemo/shed_lint.py
@@ -188,8 +188,55 @@ def lint_readme(realized_repository, lint_ctx):
 
 
 def lint_tool_dependencies_urls(realized_repository, lint_ctx):
-    
-    
+
+    def lint_urls(root, lint_ctx):
+        """Find referenced URLs and verify they are valid.
+        
+        note this function was used previously for tools (URLs in help) and tool dependency files
+        the former has been rewritten and therefore the function has been moved here
+        """
+        urls, docs = find_urls_for_xml(root)
+
+        # This is from Google Chome on macOS, current at time of writing:
+        BROWSER_USER_AGENT = "Mozilla/5.0 (Macintosh; Intel Mac OS X 11_1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/87.0.4280.141 Safari/537.36"
+
+        def validate_url(url, lint_ctx, user_agent=None):
+            is_valid = True
+            if url.startswith("http://") or url.startswith("https://"):
+                if user_agent:
+                    headers = {"User-Agent": user_agent, "Accept": "*/*"}
+                else:
+                    headers = None
+                r = None
+                try:
+                    r = requests.get(url, headers=headers, stream=True)
+                    r.raise_for_status()
+                    next(r.iter_content(1000))
+                except Exception as e:
+                    if r is not None and r.status_code == 429:
+                        # too many requests
+                        pass
+                    if r is not None and r.status_code in [403, 503] and "cloudflare" in r.text:
+                        # CloudFlare protection block
+                        pass
+                    else:
+                        is_valid = False
+                        lint_ctx.error(f"Error '{e}' accessing {url}")
+            else:
+                try:
+                    with urlopen(url) as handle:
+                        handle.read(100)
+                except Exception as e:
+                    is_valid = False
+                    lint_ctx.error(f"Error '{e}' accessing {url}")
+            if is_valid:
+                lint_ctx.info("URL OK %s" % url)
+
+        for url in urls:
+            validate_url(url, lint_ctx)
+        for url in docs:
+            validate_url(url, lint_ctx, BROWSER_USER_AGENT)
+
     path = realized_repository.real_path
     tool_dependencies = os.path.join(path, "tool_dependencies.xml")
     if not os.path.exists(tool_dependencies):