diff --git a/changelog.md b/changelog.md
index 7dd55cd..b885f9b 100644
--- a/changelog.md
+++ b/changelog.md
@@ -4,6 +4,7 @@
 
 ### Features
 
+* Signature help support.
 * Provide human readable code actions titles.
 * Add --help and --version command line flags.
 * Support providing improved completion kinds to clients.
diff --git a/src/fennel-ls/analyzer.fnl b/src/fennel-ls/analyzer.fnl
index 0739e31..b048359 100644
--- a/src/fennel-ls/analyzer.fnl
+++ b/src/fennel-ls/analyzer.fnl
@@ -39,12 +39,11 @@ find the definition `10`, but if `opts.stop-early?` is set, it would find
 "
 
 (local {: sym? : list? : sequence? : varg?} (require :fennel))
-(local utils (require :fennel-ls.utils))
+(local {: special?} (require :fennel-ls.compiler))
+(local {: get-ast-info &as utils} (require :fennel-ls.utils))
 (local files (require :fennel-ls.files))
 (local docs (require :fennel-ls.docs))
 
-(local get-ast-info utils.get-ast-info)
-
 (var search-multival nil) ;; all of the search functions are mutually recursive
 
 (λ stack-add-keys! [stack ?keys]
@@ -222,9 +221,8 @@ find the definition `10`, but if `opts.stop-early?` is set, it would find
 (λ _past? [?ast byte]
   ;; check if a byte is past an ast object
   (and (= (type ?ast) :table)
-       (get-ast-info ?ast :bytestart)
-       (< byte (get-ast-info ?ast :bytestart))
-       false))
+       (get-ast-info ?ast :byteend)
+       (< (get-ast-info ?ast :byteend) byte)))
 
 (λ contains? [?ast byte]
   ;; check if an ast contains a byte
@@ -276,12 +274,23 @@ find the definition `10`, but if `opts.stop-early?` is set, it would find
     (fcollect [i 1 (length parents)]
       (. parents (- (length parents) i -1)))))
 
+(λ find-nearest-call [server file position]
+  "Find the nearest call
+
+returns the called symbol and the argument number position points to"
+  (let [byte (utils.position->byte file.text position server.position-encoding)
+        (_ [[call] [parent]]) (find-symbol file.ast byte)]
+    (if (special? parent)
+        (values parent -1)
+        (values call -1))))
+
 (λ find-nearest-definition [server file symbol ?byte]
   (if (. file.definitions symbol)
     (. file.definitions symbol)
     (search-main server file symbol {:stop-early? true} {:byte ?byte})))
 
 {: find-symbol
+ : find-nearest-call
  : find-nearest-definition
  : search-main
  : search-name-and-scope
diff --git a/src/fennel-ls/compiler.fnl b/src/fennel-ls/compiler.fnl
index f571564..1780a69 100644
--- a/src/fennel-ls/compiler.fnl
+++ b/src/fennel-ls/compiler.fnl
@@ -6,6 +6,7 @@ compiler's plugin hook callbacks. It stores lexical info about which
 identifiers are declared / referenced in which places."
 
 (local {: sym? : list? : sequence? : table? : sym : view &as fennel} (require :fennel))
+(local {:scopes {:global {: specials}}} (require :fennel.compiler))
 (local docs (require :fennel-ls.docs))
 (local message (require :fennel-ls.message))
 (local searcher (require :fennel-ls.searcher))
@@ -13,6 +14,20 @@ identifiers are declared / referenced in which places."
 
 (local nil* (sym :nil))
 
+(fn special? [item]
+  (and (sym? item)
+       (. specials (tostring item))
+       item))
+
+(local ops {"+" 1 "-" 1 "*" 1 "/" 1 "//" 1 "%" 1 "^" 1 ">" 1 "<" 1 ">=" 1
+            "<=" 1 "=" 1 "not=" 1 ".." 1 "." 1 "and" 1 "or" 1 "band" 1
+            "bor" 1 "bxor" 1 "bnot" 1 "lshift" 1 "rshift" 1})
+
+(fn op? [item]
+  (and (sym? item)
+       (. ops (tostring item))
+       item))
+
 (fn scope? [candidate]
   ;; just checking a couple of the fields
   (and
@@ -426,4 +441,6 @@ identifiers are declared / referenced in which places."
       (set file.macro-refs macro-refs)
       (set file.macro-calls macro-calls))))
 
-{: compile}
+{: special?
+ : op?
+ : compile}
diff --git a/src/fennel-ls/formatter.fnl b/src/fennel-ls/formatter.fnl
index 864ef55..0eb2b96 100644
--- a/src/fennel-ls/formatter.fnl
+++ b/src/fennel-ls/formatter.fnl
@@ -9,6 +9,22 @@ user code. Fennel-ls doesn't support user-code formatting as of now."
 (λ code-block [str]
   (.. "```fnl\n" str "\n```"))
 
+(λ render-arg [arg]
+  (case (type arg)
+    :table (view arg {:one-line? true
+                      :prefer-colon? true})
+    _ (tostring arg)))
+
+(λ fn-signature-format [name args]
+  (let [args (case (type (?. args 1))
+               :table (icollect [_ v (ipairs args)]
+                        (render-arg v))
+               _ args)]
+    (.. "("
+        (tostring name) " "
+        (table.concat args " ")
+        ")")))
+
 (fn fn-format [special name args docstring]
   (.. (code-block (.. "("
                       (tostring special)
@@ -78,12 +94,32 @@ fntype is one of fn or λ or lambda"
       (= (type arglist) :table))
     {: fntype : arglist}))
 
+(λ signature-help-format [symbol]
+  "Return a signatureHelp lsp object
+
+  symbol can be an actual ast symbol or a binding object from a docset"
+  (case (analyze-fn symbol.definition)
+    {:name ?name :arglist ?arglist :docstring ?docstring}
+    {:label (fn-signature-format ?name ?arglist)
+     :documentation ?docstring
+     :parameters (if ?arglist
+                     (icollect [_ arg (ipairs ?arglist)]
+                       {:label (render-arg arg)}))}
+    _ (case symbol
+        {: binding :metadata {:fnl/arglist arglist :fnl/docstring docstring}}
+        {:label (fn-signature-format binding arglist)
+         :documentation docstring}
+        _ {:label (.. "ERROR: don't know how to format " (tostring symbol))
+           :documentation (code-block
+                            (view symbol {:depth 3}))})))
+
 (λ hover-format [result]
   "Format code that will appear when the user hovers over a symbol"
   {:kind "markdown"
    :value
    (case (analyze-fn result.definition)
-     {:fntype ?fntype :name ?name :arglist ?arglist :docstring ?docstring} (fn-format ?fntype ?name ?arglist ?docstring)
+     {:fntype ?fntype :name ?name :arglist ?arglist :docstring ?docstring}
+     (fn-format ?fntype ?name ?arglist ?docstring)
      _ (if (-?>> result.keys length (< 0))
          (code-block
            (.. "ERROR, I don't know how to show this "
@@ -112,5 +148,6 @@ fntype is one of fn or λ or lambda"
          :kind (. kinds (?. result :metadata :fls/itemKind))})
     (tset :documentation (hover-format result))))
 
-{: hover-format
+{: signature-help-format
+ : hover-format
  : completion-item-format}
diff --git a/src/fennel-ls/handlers.fnl b/src/fennel-ls/handlers.fnl
index 3ea6d10..b8bc15f 100644
--- a/src/fennel-ls/handlers.fnl
+++ b/src/fennel-ls/handlers.fnl
@@ -40,7 +40,9 @@ Every time the client sends a message, it gets handled by a function in the corr
                               :triggerCharacters ["(" "[" "{" "." ":" "\""]
                               :completionItem {:labelDetailsSupport false}}
          :hoverProvider {:workDoneProgress false}
-         ;; :signatureHelpProvider nil
+         :signatureHelpProvider {:workDoneProgress false
+                                 :triggerCharacters [" "]
+                                 :retriggerCharacters [" "]}
          ;; :declarationProvider nil
          :definitionProvider {:workDoneProgress false}
          ;; :typeDefinitionProvider nil
@@ -135,6 +137,19 @@ Every time the client sends a message, it gets handled by a function in the corr
         result)
       (catch _ nil))))
 
+(λ requests.textDocument/signatureHelp [server
+                                          _send
+                                          {:textDocument {: uri} : position}]
+  (let [file (files.get-by-uri server uri)]
+    (case-try (analyzer.find-nearest-call server file position)
+      (symbol active-parameter)
+      (analyzer.find-nearest-definition server file symbol)
+      {:indeterminate nil &as result}
+      (message.symbol->signature-help server file symbol
+                                      (formatter.signature-help-format result)
+                                      active-parameter)
+      (catch _ nil))))
+
 (λ requests.textDocument/hover [server _send {: position :textDocument {: uri}}]
   (let [file (files.get-by-uri server uri)
         byte (utils.position->byte file.text position server.position-encoding)]
diff --git a/src/fennel-ls/lint.fnl b/src/fennel-ls/lint.fnl
index e29e8f0..168d202 100644
--- a/src/fennel-ls/lint.fnl
+++ b/src/fennel-ls/lint.fnl
@@ -4,7 +4,7 @@ the `file.diagnostics` field, filling it with diagnostics."
 
 (local {: sym? : list? : table? : view
         : sym : list &as fennel} (require :fennel))
-(local {:scopes {:global {: specials}}} (require :fennel.compiler))
+(local {: special? : op?} (require :fennel-ls.compiler))
 (local analyzer (require :fennel-ls.analyzer))
 (local message (require :fennel-ls.message))
 (local utils (require :fennel-ls.utils))
@@ -16,20 +16,6 @@ the `file.diagnostics` field, filling it with diagnostics."
 (fn diagnostic [self quickfix]
   (setmetatable {: self : quickfix} diagnostic-mt))
 
-(local ops {"+" 1 "-" 1 "*" 1 "/" 1 "//" 1 "%" 1 "^" 1 ">" 1 "<" 1 ">=" 1
-            "<=" 1 "=" 1 "not=" 1 ".." 1 "." 1 "and" 1 "or" 1 "band" 1
-            "bor" 1 "bxor" 1 "bnot" 1 "lshift" 1 "rshift" 1})
-
-(fn special? [item]
-  (and (sym? item)
-       (. specials (tostring item))
-       item))
-
-(fn op? [item]
-  (and (sym? item)
-       (. ops (tostring item))
-       item))
-
 (fn could-be-rewritten-as-sym? [str]
   (and (= :string (type str)) (not (str:find "^%d"))
        (not (str:find "[^!$%*+/0-9<=>?A-Z\\^_a-z|\128-\255-]"))))
diff --git a/src/fennel-ls/message.fnl b/src/fennel-ls/message.fnl
index 9b3205a..a142a6c 100644
--- a/src/fennel-ls/message.fnl
+++ b/src/fennel-ls/message.fnl
@@ -91,6 +91,11 @@ LSP json objects."
      :kind ?kind
      :edit {:changes {uri (diagnostic.quickfix)}}}))
 
+(λ symbol->signature-help [_server _file _call signature active-parameter]
+  {:signatures [signature]
+   :activeSignature 0
+   :activeParameter active-parameter})
+
 (λ multisym->range [server file ast n]
   (let [spl (utils.multi-sym-split ast)
         n (if (< n 0) (+ n 1 (length spl)) n)]
@@ -129,6 +134,7 @@ LSP json objects."
  : create-error
  : ast->range
  : diagnostic->code-action
+ : symbol->signature-help
  : multisym->range
  : range-and-uri
  : diagnostics
diff --git a/test/signature-help.fnl b/test/signature-help.fnl
new file mode 100644
index 0000000..f3e459d
--- /dev/null
+++ b/test/signature-help.fnl
@@ -0,0 +1,76 @@
+(local faith (require :faith))
+(local {: view} (require :fennel))
+(local {: create-client} (require :test.utils))
+
+(λ check-signature [expected response]
+  (case response
+    {:signatures [{:label signature}]}
+    (faith.= expected.signature signature)
+    ;; fail
+    _ (faith.is nil (.. "Invalid response: " (view response)))))
+
+(fn check [file-contents expected]
+  (let [{: client : uri : cursor} (create-client file-contents)
+        [{: result}] (client:signature-help uri cursor)]
+    (check-signature expected result)))
+
+(fn test-fn-definition []
+  (check "(fn func [arg1 arg2] (print :hello))
+          (func|)"
+         {:signature "(func arg1 arg2)"})
+
+  (check "(fn func [arg1 arg2] (print :hello))
+          (func |)"
+         {:signature "(func arg1 arg2)"})
+
+  (check "(fn func [arg1 arg2] (print :hello))
+          (func a1|)"
+         {:signature "(func arg1 arg2)"})
+
+  (check "(fn func [arg1 arg2] (print :hello))
+          (func a|1 a2)"
+         {:signature "(func arg1 arg2)"})
+
+  (check "(fn func [arg1 arg2] (print :hello))
+          (func a1 a2|)"
+         {:signature "(func arg1 arg2)"})
+
+  (check "(fn func [arg1 arg2] (print :hello))
+          (func a1 a|2)"
+         {:signature "(func arg1 arg2)"}))
+
+(fn test-lua-builtin []
+  (check "(error msg lvl|)"
+         {:signature "(error message ?level)"}))
+
+(fn test-multisym []
+  (check "(table.concat tbl s|)"
+         {:signature "(table.concat list ?sep ?i ?j)"}))
+
+(fn test-destructuring-arg []
+  (check "(fn dstr [{:field name} arg2] {})
+          (dstr |)"
+         {:signature "(dstr {:field name} arg2)"})
+
+  (check "(fn dstr [{:field name} arg2] {})
+          (dstr arg1 ar|)"
+         {:signature "(dstr {:field name} arg2)"}))
+
+(fn test-special []
+  (check "(each |)"
+         {:signature "(each [key value (iterator)] ...)"})
+
+  (check "(each [|])"
+         {:signature "(each [key value (iterator)] ...)"})
+
+  (check "(each [k val|])"
+         {:signature "(each [key value (iterator)] ...)"})
+
+  (check "(each [33|])"
+         {:signature "(each [key value (iterator)] ...)"}))
+
+{: test-fn-definition
+ : test-lua-builtin
+ : test-multisym
+ : test-destructuring-arg
+ : test-special}
diff --git a/test/utils/client.fnl b/test/utils/client.fnl
index 37a07d2..d1dc210 100644
--- a/test/utils/client.fnl
+++ b/test/utils/client.fnl
@@ -55,6 +55,14 @@
      {: position
       :textDocument {:uri file}})))
 
+(fn signature-help [self file position]
+  (dispatch.handle*
+    self.server
+    (message.create-request (next-id! self)
+                            :textDocument/signatureHelp
+                            {: position
+                             :textDocument {:uri file}})))
+
 (fn rename [self file position newName]
   (dispatch.handle* self.server
     (message.create-request (next-id! self) :textDocument/rename
@@ -83,6 +91,7 @@
              : hover
              : references
              : document-highlight
+             : signature-help
              : rename
              : code-action
              : did-save}})