Add fields table to agency-index.json docs

Signed-off-by: Natalia Luzuriaga <natalia.luzuriaga@cms.hhs.gov>

Author: natalialuzuriaga

docs/agency-index.md

@@ -1,8 +1,8 @@
-## agency-index.json
+# agency-index.json
 
 The SHARE IT Act requires federal agencies to publish metadata for their software projects. This metadata is compiled into an **agency-index.json** file, which serves as a centralized inventory of the agency's software portfolio.
 
-View the agency-index.json schema here: https://github.com/DSACMS/gov-codejson/tree/main/schemas/agency-index/schema-2.0.0.json
+## Generate an agency-index.json file for submission
 
 To create an agency-index.json:
 1. Identify GitHub organizations and other platforms where source code is hosted
@@ -13,4 +13,64 @@ To create an agency-index.json:
   - Agency's top level domain (TLD)
   - A GitHub repository
 
+## agency-index.json Fields
+
+<table>
+  <thead>
+    <tr>
+      <th>Field</th>
+      <th>Presence</th>
+      <th>Type</th>
+      <th>Description</th>
+      <th>Options/Examples</th>
+    </tr>
+  </thead>
+  <tbody>
+    <tr>
+      <td>agency</td>
+      <td>required</td>
+      <td>str</td>
+      <td>The agency acronym for Clinger Cohen Act agency, as defined by the United States Government Manual.</td>
+      <td></td>
+    </tr>
+    <tr>
+      <td>measurementType/method</td>
+      <td>required</td>
+      <td>str</td>
+      <td>An enumerated list of methods for measuring the open source requirement.</td>
+      <td>
+        - linesOfCode
+        - modules
+        - cost
+        - projects
+        - systems
+        - other
+      </td>
+    </tr>
+    <tr>
+      <td>measurementType/ifOther</td>
+      <td>optional</td>
+      <td>str</td>
+      <td>A one- or two- sentence description of the measurement type used, if 'other' is selected as the value of 'method' field.</td>
+      <td></td>
+    </tr>
+    <tr>
+      <td>releases</td>
+      <td>required</td>
+      <td>array</td>
+      <td>An array of code.json objects containing each versioned source code release made available. </td>
+      <td></td>
+    </tr>
+    <tr>
+      <td>version</td>
+      <td>required</td>
+      <td>str</td>
+      <td>The version of the metadata schema in use. Implements semantic versioning 2.0.0 rules as defined at http://semver.org.</td>
+      <td></td>
+    </tr>
+  <tbody>
+<table>
+
+View the agency-index.json schema here: https://github.com/DSACMS/gov-codejson/tree/main/schemas/agency-index/schema-2.0.0.json
+
 More examples of agency index files can be found here: https://github.com/DSACMS/code-gov/tree/main/agency-indexes