diff --git a/slither/core/slither_core.py b/slither/core/slither_core.py
index 66b8fc430..cba86e56e 100644
--- a/slither/core/slither_core.py
+++ b/slither/core/slither_core.py
@@ -443,7 +443,7 @@ class SlitherCore(Context):
 
         return True
 
-    def load_previous_results(self):
+    def load_previous_results(self) -> None:
         filename = self._previous_results_filename
         try:
             if os.path.isfile(filename):
@@ -456,7 +456,7 @@ class SlitherCore(Context):
         except json.decoder.JSONDecodeError:
             logger.error(red(f"Impossible to decode {filename}. Consider removing the file"))
 
-    def write_results_to_hide(self):
+    def write_results_to_hide(self) -> None:
         if not self._results_to_hide:
             return
         filename = self._previous_results_filename
@@ -464,7 +464,7 @@ class SlitherCore(Context):
             results = self._results_to_hide + self._previous_results
             json.dump(results, f)
 
-    def save_results_to_hide(self, results: List[Dict]):
+    def save_results_to_hide(self, results: List[Dict]) -> None:
         self._results_to_hide += results
 
     def add_path_to_filter(self, path: str):
diff --git a/slither/slither.py b/slither/slither.py
index 45d99906f..93cf16394 100644
--- a/slither/slither.py
+++ b/slither/slither.py
@@ -11,6 +11,7 @@ from slither.detectors.abstract_detector import AbstractDetector, DetectorClassi
 from slither.exceptions import SlitherError
 from slither.printers.abstract_printer import AbstractPrinter
 from slither.solc_parsing.slither_compilation_unit_solc import SlitherCompilationUnitSolc
+from slither.utils.output import Output
 
 logger = logging.getLogger("Slither")
 logging.basicConfig()
@@ -206,7 +207,7 @@ class Slither(SlitherCore):  # pylint: disable=too-many-instance-attributes
         self.write_results_to_hide()
         return results
 
-    def run_printers(self):
+    def run_printers(self) -> List[Output]:
         """
         :return: List of registered printers outputs.
         """
diff --git a/slither/tools/doctor/__main__.py b/slither/tools/doctor/__main__.py
index b9b4c5497..f401781a7 100644
--- a/slither/tools/doctor/__main__.py
+++ b/slither/tools/doctor/__main__.py
@@ -26,7 +26,7 @@ def parse_args() -> argparse.Namespace:
     return parser.parse_args()
 
 
-def main():
+def main() -> None:
     # log on stdout to keep output in order
     logging.basicConfig(stream=sys.stdout, level=logging.DEBUG, force=True)
 
diff --git a/slither/tools/erc_conformance/__main__.py b/slither/tools/erc_conformance/__main__.py
index ef594a7c6..4f0c19f80 100644
--- a/slither/tools/erc_conformance/__main__.py
+++ b/slither/tools/erc_conformance/__main__.py
@@ -1,10 +1,11 @@
 import argparse
 import logging
 from collections import defaultdict
-from typing import Any, Dict, List
+from typing import Any, Dict, List, Callable, Optional
 
 from crytic_compile import cryticparser
 from slither import Slither
+from slither.core.declarations import Contract
 from slither.utils.erc import ERCS
 from slither.utils.output import output_to_json
 from .erc.ercs import generic_erc_checks
@@ -24,7 +25,10 @@ logger.addHandler(ch)
 logger.handlers[0].setFormatter(formatter)
 logger.propagate = False
 
-ADDITIONAL_CHECKS = {"ERC20": check_erc20, "ERC1155": check_erc1155}
+ADDITIONAL_CHECKS: Dict[str, Callable[[Contract, Dict[str, List]], Dict[str, List]]] = {
+    "ERC20": check_erc20,
+    "ERC1155": check_erc1155,
+}
 
 
 def parse_args() -> argparse.Namespace:
diff --git a/slither/tools/erc_conformance/erc/erc1155.py b/slither/tools/erc_conformance/erc/erc1155.py
index fceb4e242..34bb18bfb 100644
--- a/slither/tools/erc_conformance/erc/erc1155.py
+++ b/slither/tools/erc_conformance/erc/erc1155.py
@@ -1,12 +1,14 @@
 import logging
+from typing import Dict, List, Optional
 
+from slither.core.declarations import Contract
 from slither.slithir.operations import EventCall
 from slither.utils import output
 
 logger = logging.getLogger("Slither-conformance")
 
 
-def events_safeBatchTransferFrom(contract, ret):
+def events_safeBatchTransferFrom(contract: Contract, ret: Dict[str, List]) -> None:
     function = contract.get_function_from_signature(
         "safeBatchTransferFrom(address,address,uint256[],uint256[],bytes)"
     )
@@ -44,7 +46,9 @@ def events_safeBatchTransferFrom(contract, ret):
         )
 
 
-def check_erc1155(contract, ret, explored=None):
+def check_erc1155(
+    contract: Contract, ret: Dict[str, List], explored: Optional[bool] = None
+) -> Dict[str, List]:
     if explored is None:
         explored = set()
 
diff --git a/slither/tools/erc_conformance/erc/erc20.py b/slither/tools/erc_conformance/erc/erc20.py
index 720b08322..6ee243515 100644
--- a/slither/tools/erc_conformance/erc/erc20.py
+++ b/slither/tools/erc_conformance/erc/erc20.py
@@ -1,11 +1,13 @@
 import logging
+from typing import Dict, List, Optional
 
+from slither.core.declarations import Contract
 from slither.utils import output
 
 logger = logging.getLogger("Slither-conformance")
 
 
-def approval_race_condition(contract, ret):
+def approval_race_condition(contract: Contract, ret: Dict[str, List]) -> None:
     increaseAllowance = contract.get_function_from_signature("increaseAllowance(address,uint256)")
 
     if not increaseAllowance:
@@ -27,7 +29,9 @@ def approval_race_condition(contract, ret):
         )
 
 
-def check_erc20(contract, ret, explored=None):
+def check_erc20(
+    contract: Contract, ret: Dict[str, List], explored: Optional[bool] = None
+) -> Dict[str, List]:
     if explored is None:
         explored = set()
 
diff --git a/slither/tools/kspec_coverage/analysis.py b/slither/tools/kspec_coverage/analysis.py
index 3d513d22f..514bfa58f 100755
--- a/slither/tools/kspec_coverage/analysis.py
+++ b/slither/tools/kspec_coverage/analysis.py
@@ -1,8 +1,12 @@
 import re
 import logging
-from typing import Set, Tuple
+from argparse import Namespace
+from typing import Set, Tuple, List, Dict, Union, Optional, Callable
 
-from slither.core.declarations import Function
+from slither import Slither
+from slither.core.compilation_unit import SlitherCompilationUnit
+from slither.core.declarations import Function, FunctionContract
+from slither.core.variables.state_variable import StateVariable
 from slither.core.variables.variable import Variable
 from slither.utils.colors import yellow, green, red
 from slither.utils import output
@@ -54,13 +58,15 @@ def _get_all_covered_kspec_functions(target: str) -> Set[Tuple[str, str]]:
     return covered_functions
 
 
-def _get_slither_functions(slither):
+def _get_slither_functions(
+    slither: SlitherCompilationUnit,
+) -> Dict[Tuple[str, str], Union[FunctionContract, StateVariable]]:
     # Use contract == contract_declarer to avoid dupplicate
-    all_functions_declared = [
+    all_functions_declared: List[Union[FunctionContract, StateVariable]] = [
         f
         for f in slither.functions
         if (
-            f.contract == f.contract_declarer
+            (isinstance(f, FunctionContract) and f.contract == f.contract_declarer)
             and f.is_implemented
             and not f.is_constructor
             and not f.is_constructor_variables
@@ -79,7 +85,12 @@ def _get_slither_functions(slither):
     return slither_functions
 
 
-def _generate_output(kspec, message, color, generate_json):
+def _generate_output(
+    kspec: List[Union[FunctionContract, StateVariable]],
+    message: str,
+    color: Callable[[str], str],
+    generate_json: bool,
+) -> Optional[Dict]:
     info = ""
     for function in kspec:
         info += f"{message} {function.contract.name}.{function.full_name}\n"
@@ -94,7 +105,9 @@ def _generate_output(kspec, message, color, generate_json):
     return None
 
 
-def _generate_output_unresolved(kspec, message, color, generate_json):
+def _generate_output_unresolved(
+    kspec: Set[Tuple[str, str]], message: str, color: Callable[[str], str], generate_json: bool
+) -> Optional[Dict]:
     info = ""
     for contract, function in kspec:
         info += f"{message} {contract}.{function}\n"
@@ -107,17 +120,19 @@ def _generate_output_unresolved(kspec, message, color, generate_json):
     return None
 
 
-def _run_coverage_analysis(args, slither, kspec_functions):
+def _run_coverage_analysis(
+    args, slither: SlitherCompilationUnit, kspec_functions: Set[Tuple[str, str]]
+) -> None:
     # Collect all slither functions
     slither_functions = _get_slither_functions(slither)
 
     # Determine which klab specs were not resolved.
     slither_functions_set = set(slither_functions)
     kspec_functions_resolved = kspec_functions & slither_functions_set
-    kspec_functions_unresolved = kspec_functions - kspec_functions_resolved
+    kspec_functions_unresolved: Set[Tuple[str, str]] = kspec_functions - kspec_functions_resolved
 
-    kspec_missing = []
-    kspec_present = []
+    kspec_missing: List[Union[FunctionContract, StateVariable]] = []
+    kspec_present: List[Union[FunctionContract, StateVariable]] = []
 
     for slither_func_desc in sorted(slither_functions_set):
         slither_func = slither_functions[slither_func_desc]
@@ -130,13 +145,13 @@ def _run_coverage_analysis(args, slither, kspec_functions):
     logger.info("## Check for functions coverage")
     json_kspec_present = _generate_output(kspec_present, "[✓]", green, args.json)
     json_kspec_missing_functions = _generate_output(
-        [f for f in kspec_missing if isinstance(f, Function)],
+        [f for f in kspec_missing if isinstance(f, FunctionContract)],
         "[ ] (Missing function)",
         red,
         args.json,
     )
     json_kspec_missing_variables = _generate_output(
-        [f for f in kspec_missing if isinstance(f, Variable)],
+        [f for f in kspec_missing if isinstance(f, StateVariable)],
         "[ ] (Missing variable)",
         yellow,
         args.json,
@@ -159,11 +174,11 @@ def _run_coverage_analysis(args, slither, kspec_functions):
         )
 
 
-def run_analysis(args, slither, kspec_arg):
+def run_analysis(args: Namespace, slither: SlitherCompilationUnit, kspec_arg: str) -> None:
     # Get all of our kspec'd functions (tuple(contract_name, function_name)).
     if "," in kspec_arg:
         kspecs = kspec_arg.split(",")
-        kspec_functions = set()
+        kspec_functions: Set[Tuple[str, str]] = set()
         for kspec in kspecs:
             kspec_functions |= _get_all_covered_kspec_functions(kspec)
     else:
diff --git a/slither/tools/mutator/__main__.py b/slither/tools/mutator/__main__.py
index 78b86d681..27e396d0b 100644
--- a/slither/tools/mutator/__main__.py
+++ b/slither/tools/mutator/__main__.py
@@ -72,7 +72,7 @@ class ListMutators(argparse.Action):  # pylint: disable=too-few-public-methods
 ###################################################################################
 
 
-def main():
+def main() -> None:
 
     args = parse_args()
 
diff --git a/slither/tools/mutator/mutators/MIA.py b/slither/tools/mutator/mutators/MIA.py
index 54ca0ec1c..405888f8b 100644
--- a/slither/tools/mutator/mutators/MIA.py
+++ b/slither/tools/mutator/mutators/MIA.py
@@ -1,3 +1,5 @@
+from typing import Dict
+
 from slither.core.cfg.node import NodeType
 from slither.formatters.utils.patches import create_patch
 from slither.tools.mutator.mutators.abstract_mutator import AbstractMutator, FaultNature, FaultClass
@@ -9,13 +11,13 @@ class MIA(AbstractMutator):  # pylint: disable=too-few-public-methods
     FAULTCLASS = FaultClass.Checking
     FAULTNATURE = FaultNature.Missing
 
-    def _mutate(self):
+    def _mutate(self) -> Dict:
 
-        result = {}
+        result: Dict = {}
 
         for contract in self.slither.contracts:
 
-            for function in contract.functions_declared + contract.modifiers_declared:
+            for function in contract.functions_declared + list(contract.modifiers_declared):
 
                 for node in function.nodes:
                     if node.type == NodeType.IF:
diff --git a/slither/tools/mutator/mutators/MVIE.py b/slither/tools/mutator/mutators/MVIE.py
index 8f8cc11bf..a16a8252e 100644
--- a/slither/tools/mutator/mutators/MVIE.py
+++ b/slither/tools/mutator/mutators/MVIE.py
@@ -1,4 +1,7 @@
+from typing import Dict
+
 from slither.core.expressions import Literal
+from slither.core.variables.variable import Variable
 from slither.tools.mutator.mutators.abstract_mutator import AbstractMutator, FaultNature, FaultClass
 from slither.tools.mutator.utils.generic_patching import remove_assignement
 
@@ -9,10 +12,10 @@ class MVIE(AbstractMutator):  # pylint: disable=too-few-public-methods
     FAULTCLASS = FaultClass.Assignement
     FAULTNATURE = FaultNature.Missing
 
-    def _mutate(self):
-
-        result = {}
+    def _mutate(self) -> Dict:
 
+        result: Dict = {}
+        variable: Variable
         for contract in self.slither.contracts:
 
             # Create fault for state variables declaration
@@ -25,7 +28,7 @@ class MVIE(AbstractMutator):  # pylint: disable=too-few-public-methods
                     if not isinstance(variable.expression, Literal):
                         remove_assignement(variable, contract, result)
 
-            for function in contract.functions_declared + contract.modifiers_declared:
+            for function in contract.functions_declared + list(contract.modifiers_declared):
                 for variable in function.local_variables:
                     if variable.initialized and not isinstance(variable.expression, Literal):
                         remove_assignement(variable, contract, result)
diff --git a/slither/tools/mutator/mutators/MVIV.py b/slither/tools/mutator/mutators/MVIV.py
index dac34da28..d4a7c5486 100644
--- a/slither/tools/mutator/mutators/MVIV.py
+++ b/slither/tools/mutator/mutators/MVIV.py
@@ -1,4 +1,7 @@
+from typing import Dict
+
 from slither.core.expressions import Literal
+from slither.core.variables.variable import Variable
 from slither.tools.mutator.mutators.abstract_mutator import AbstractMutator, FaultNature, FaultClass
 from slither.tools.mutator.utils.generic_patching import remove_assignement
 
@@ -9,9 +12,10 @@ class MVIV(AbstractMutator):  # pylint: disable=too-few-public-methods
     FAULTCLASS = FaultClass.Assignement
     FAULTNATURE = FaultNature.Missing
 
-    def _mutate(self):
+    def _mutate(self) -> Dict:
 
-        result = {}
+        result: Dict = {}
+        variable: Variable
 
         for contract in self.slither.contracts:
 
@@ -25,7 +29,7 @@ class MVIV(AbstractMutator):  # pylint: disable=too-few-public-methods
                     if isinstance(variable.expression, Literal):
                         remove_assignement(variable, contract, result)
 
-            for function in contract.functions_declared + contract.modifiers_declared:
+            for function in contract.functions_declared + list(contract.modifiers_declared):
                 for variable in function.local_variables:
                     if variable.initialized and isinstance(variable.expression, Literal):
                         remove_assignement(variable, contract, result)
diff --git a/slither/tools/mutator/utils/command_line.py b/slither/tools/mutator/utils/command_line.py
index 9799fd488..fdef145f3 100644
--- a/slither/tools/mutator/utils/command_line.py
+++ b/slither/tools/mutator/utils/command_line.py
@@ -1,7 +1,7 @@
 from slither.utils.myprettytable import MyPrettyTable
 
 
-def output_mutators(mutators_classes):
+def output_mutators(mutators_classes: List[Type[AbstractMutator]]) -> None:
     mutators_list = []
     for detector in mutators_classes:
         argument = detector.NAME
diff --git a/slither/tools/similarity/__main__.py b/slither/tools/similarity/__main__.py
index 86673fccd..00caa3fbd 100755
--- a/slither/tools/similarity/__main__.py
+++ b/slither/tools/similarity/__main__.py
@@ -7,7 +7,7 @@ import sys
 from crytic_compile import cryticparser
 
 from slither.tools.similarity.info import info
-from slither.tools.similarity.test import test
+from slither.tools.similarity import test
 from slither.tools.similarity.train import train
 from slither.tools.similarity.plot import plot
 
diff --git a/slither/tools/similarity/encode.py b/slither/tools/similarity/encode.py
index d08086282..48700ec4a 100644
--- a/slither/tools/similarity/encode.py
+++ b/slither/tools/similarity/encode.py
@@ -1,5 +1,6 @@
 import logging
 import os
+from typing import Optional, Tuple, List
 
 from slither import Slither
 from slither.core.declarations import (
@@ -60,7 +61,7 @@ slither_logger = logging.getLogger("Slither")
 slither_logger.setLevel(logging.CRITICAL)
 
 
-def parse_target(target):
+def parse_target(target: Optional[str]) -> Tuple[Optional[str], Optional[str]]:
     if target is None:
         return None, None
 
@@ -68,9 +69,9 @@ def parse_target(target):
     if len(parts) == 1:
         return None, parts[0]
     if len(parts) == 2:
-        return parts
+        return parts[0], parts[1]
     simil_logger.error("Invalid target. It should be 'function' or 'Contract.function'")
-    return None
+    return None, None
 
 
 def load_and_encode(infile: str, vmodel, ext=None, nsamples=None, **kwargs):
@@ -88,7 +89,9 @@ def load_and_encode(infile: str, vmodel, ext=None, nsamples=None, **kwargs):
     return r
 
 
-def load_contracts(dirname, ext=None, nsamples=None):
+def load_contracts(
+    dirname: str, ext: Optional[str] = None, nsamples: Optional[int] = None
+) -> List[str]:
     r = []
     walk = list(os.walk(dirname))
     for x, y, files in walk:
diff --git a/slither/tools/similarity/test.py b/slither/tools/similarity/test.py
index 76229d5bf..145e50321 100755
--- a/slither/tools/similarity/test.py
+++ b/slither/tools/similarity/test.py
@@ -2,6 +2,7 @@ import logging
 import operator
 import sys
 import traceback
+from argparse import Namespace
 
 from slither.tools.similarity.encode import encode_contract, load_and_encode, parse_target
 from slither.tools.similarity.model import load_model
@@ -10,7 +11,7 @@ from slither.tools.similarity.similarity import similarity
 logger = logging.getLogger("Slither-simil")
 
 
-def test(args):
+def est(args: Namespace) -> None:
 
     try:
         model = args.model