diff --git a/.github/workflows/check-witx.yaml b/.github/workflows/check-witx.yaml
new file mode 100644
index 0000000..d4b71e2
--- /dev/null
+++ b/.github/workflows/check-witx.yaml
@@ -0,0 +1,26 @@
+name: Check Witx
+
+on: [push, pull_request]
+
+jobs:
+  Witx:
+    name: "Check Witx"
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v2
+
+      - name: Generate markdown
+        uses: NodeFactoryIo/witx-md-generator-action@master
+        with:
+          witxGlobPath: spec/witx/**/*.witx
+
+      - name: Check if there are changes
+        id: changes
+        uses: UnicornGlobal/has-changes-action@v1.0.11
+
+      - name: Process changes
+        if: steps.changes.outputs.changed == 1
+        run: exit 1
diff --git a/spec/witx/README.md b/spec/witx/README.md
new file mode 100644
index 0000000..8f4beee
--- /dev/null
+++ b/spec/witx/README.md
@@ -0,0 +1,15 @@
+## Generating Markdown
+
+Generating Markdown is done via tool from WASI [repo](https://github.com/WebAssembly/WASI/tree/master/tools/witx):
+
+```bash
+cargo run witx docs "path/**/*.witx"
+```
+
+### Docker
+
+Also available is a docker image with prepackaged cli:
+
+```bash
+docker run -v /path:/usr/src/witx  nodefactory/witx docs "path/**/*.witx"
+```
diff --git a/spec/witx/w3.md b/spec/witx/w3.md
new file mode 100644
index 0000000..1353777
--- /dev/null
+++ b/spec/witx/w3.md
@@ -0,0 +1,123 @@
+# Types
+# Modules
+## <a href="#w3" name="w3"></a> w3
+### Imports
+### Functions
+
+---
+
+#### <a href="#_w3_init" name="_w3_init"></a> `_w3_init()`
+Init w3
+
+##### Params
+##### Results
+
+---
+
+#### <a href="#_w3_invoke" name="_w3_invoke"></a> `_w3_invoke(name_size: u64, args_size: u32)`
+Invoke call
+
+##### Params
+- <a href="#_w3_invoke.name_size" name="_w3_invoke.name_size"></a> `name_size`: `u64`
+
+- <a href="#_w3_invoke.args_size" name="_w3_invoke.args_size"></a> `args_size`: `u32`
+
+##### Results
+
+---
+
+#### <a href="#__w3_invoke_args" name="__w3_invoke_args"></a> `__w3_invoke_args(name_ptr: s32, args_ptr: s32)`
+Get Invoke Arguments
+
+##### Params
+- <a href="#__w3_invoke_args.name_ptr" name="__w3_invoke_args.name_ptr"></a> `name_ptr`: `s32`
+
+- <a href="#__w3_invoke_args.args_ptr" name="__w3_invoke_args.args_ptr"></a> `args_ptr`: `s32`
+
+##### Results
+
+---
+
+#### <a href="#__w3_invoke_result" name="__w3_invoke_result"></a> `__w3_invoke_result(ptr: s32, len: u64)`
+Set Invoke Arguments
+
+##### Params
+- <a href="#__w3_invoke_result.ptr" name="__w3_invoke_result.ptr"></a> `ptr`: `s32`
+
+- <a href="#__w3_invoke_result.len" name="__w3_invoke_result.len"></a> `len`: `u64`
+
+##### Results
+
+---
+
+#### <a href="#__w3_invoke_error" name="__w3_invoke_error"></a> `__w3_invoke_error(ptr: s32, len: u64)`
+Set Invoke Error
+
+##### Params
+- <a href="#__w3_invoke_error.ptr" name="__w3_invoke_error.ptr"></a> `ptr`: `s32`
+
+- <a href="#__w3_invoke_error.len" name="__w3_invoke_error.len"></a> `len`: `u64`
+
+##### Results
+
+---
+
+#### <a href="#__w3_query" name="__w3_query"></a> `__w3_query(uri_ptr: s32, uri_len: u64, query_ptr: s32, query_len: u64, args_ptr: s32, args_len: u64) -> s8`
+Query API
+
+##### Params
+- <a href="#__w3_query.uri_ptr" name="__w3_query.uri_ptr"></a> `uri_ptr`: `s32`
+
+- <a href="#__w3_query.uri_len" name="__w3_query.uri_len"></a> `uri_len`: `u64`
+
+- <a href="#__w3_query.query_ptr" name="__w3_query.query_ptr"></a> `query_ptr`: `s32`
+
+- <a href="#__w3_query.query_len" name="__w3_query.query_len"></a> `query_len`: `u64`
+
+- <a href="#__w3_query.args_ptr" name="__w3_query.args_ptr"></a> `args_ptr`: `s32`
+
+- <a href="#__w3_query.args_len" name="__w3_query.args_len"></a> `args_len`: `u64`
+
+##### Results
+- <a href="#__w3_query.res" name="__w3_query.res"></a> `res`: `s8`
+
+
+---
+
+#### <a href="#__w3_query_result_len" name="__w3_query_result_len"></a> `__w3_query_result_len() -> u64`
+Query Result
+
+##### Params
+##### Results
+- <a href="#__w3_query_result_len.res" name="__w3_query_result_len.res"></a> `res`: `u64`
+
+
+---
+
+#### <a href="#__w3_query_result" name="__w3_query_result"></a> `__w3_query_result(ptr: s32)`
+Query Result
+
+##### Params
+- <a href="#__w3_query_result.ptr" name="__w3_query_result.ptr"></a> `ptr`: `s32`
+
+##### Results
+
+---
+
+#### <a href="#__w3_query_error_len" name="__w3_query_error_len"></a> `__w3_query_error_len() -> u64`
+Query Error
+
+##### Params
+##### Results
+- <a href="#__w3_query_error_len.res" name="__w3_query_error_len.res"></a> `res`: `u64`
+
+
+---
+
+#### <a href="#__w3_query_error" name="__w3_query_error"></a> `__w3_query_error(ptr: s32)`
+Query Error
+
+##### Params
+- <a href="#__w3_query_error.ptr" name="__w3_query_error.ptr"></a> `ptr`: `s32`
+
+##### Results
diff --git a/spec/witx/w3.witx b/spec/witx/w3.witx
new file mode 100644
index 0000000..408c61c
--- /dev/null
+++ b/spec/witx/w3.witx
@@ -0,0 +1,57 @@
+(module $w3
+  ;;; Init w3
+  (@interface func (export "_w3_init"))
+
+  ;;; Invoke call
+  (@interface func (export "_w3_invoke")
+    (param $name_size u64)
+    (param $args_size u32)
+  )
+
+  ;;; Get Invoke Arguments
+  (@interface func (export "__w3_invoke_args")
+    (param $name_ptr s32)
+    (param $args_ptr s32)
+  )
+
+  ;;; Set Invoke Arguments
+  (@interface func (export "__w3_invoke_result")
+    (param $ptr s32)
+    (param $len u64)
+  )
+
+  ;;; Set Invoke Error
+  (@interface func (export "__w3_invoke_error")
+    (param $ptr s32)
+    (param $len u64)
+  )
+
+  ;;; Query API
+  (@interface func (export "__w3_query")
+    (param $uri_ptr s32)
+    (param $uri_len u64)
+    (param $query_ptr s32)
+    (param $query_len u64)
+    (param $args_ptr s32)
+    (param $args_len u64)
+    (result $res s8)
+  )
+
+  ;;; Query Result
+  (@interface func (export "__w3_query_result_len")
+    (result $res u64)
+  )
+  ;;; Query Result
+  (@interface func (export "__w3_query_result")
+    (param $ptr s32)
+  )
+
+  ;;; Query Error
+  (@interface func (export "__w3_query_error_len")
+    (result $res u64)
+  )
+  ;;; Query Error
+  (@interface func (export "__w3_query_error")
+    (param $ptr s32)
+  )
+)