Add metadata docs

docs/blocks/api_call_tool.mdx

@@ -24,4 +24,11 @@ Headers | Valid JSON object of the headers to be sent with the request. i.e. `{"
 Authorize | Whether to authorize the request with organization secret. | Default: `false`
 
 ---
-
+
+## Parameters interpolation
+
+You can use parameters in the `URL` and `headers` fields.
+
+To use a parameter specified in `Parameters` field, enclose it within `{{}}`. For example, if you have a parameter named `id`, you can use it in the URL as `https://example.com/posts/{{id}}`.
+
+In order to inject secret or [Metadata](../../docs/workflows/metadata) values, use `{{secrets.secret_name}}` or `{{metadata.metadata_name}}` respectively.

docs/guides/05-api-call-tool.mdx

@@ -1,7 +1,7 @@
 ---
 title: Api Call Tool
 ---
-import {Video} from "/src/components/Video";
+import { Video } from "/src/components/Video";
 
 # Make an API Call to external APIs
 
@@ -51,7 +51,7 @@ As you can see, we have specified in the parameters that the [Api Call Tool](doc
 
 :::tip
 
-Similarly, you can use parameters in headers just like we did with the URL!
+Similarly, you can use parameters in headers just like we did with the URL! Read more about it in the [Api Call Tool](docs/blocks/api_call_tool.mdx#Parameters-interpolation) documentation.
 
 :::
 

docs/workflows/metadata.mdx

@@ -0,0 +1,15 @@
+---
+title: Metadata
+---
+
+import { Video } from "/src/components/Video";
+
+Workflow metadata is a powerful feature that allows you to store and retrieve information throught your workflow execution.
+Metadata is stored in the pipeline run context and can be interpolated in [Api Call Tool](docs/blocks/api_call_tool.mdx#Parameters-interpolation) block
+or in `X-Buildel-Context` header in [Api Call Tool](docs/blocks/api_call_tool.mdx) and [Webhook Output](docs/blocks/webhook_output.mdx) HTTP request.
+
+You can send metadata via websocket or http request on pipeline start.
+
+<Video type="video/webm" src="/mdx-assets/workflows/metadata/metadata_demo_07.webm"/>
+
+---