Made context_propagation_only dynamic (#830)

specs/agents/transport.md

@@ -71,6 +71,13 @@ would otherwise consider the data as being compressed (due to the `Content-Encod
 
 ### `context_propagation_only` configuration
 
+|                |   |
+|----------------|---|
+| Type           | `boolean` |
+| Default        | `false` |
+| Dynamic        | `true` |
+| Central config | `true` |
+
 Agents MAY implement this configuration option.
 `context_propagation_only` is a boolean configuration option to have an APM
 agent perform trace-context propagation and log correlation *only*; and to
@@ -82,14 +89,15 @@ Agents that implement this configuration option:
 
 - MUST continue to propagate trace headers (`traceparent`, `tracestate`, etc.)
   per normal;
+- MUST start a trace-id if no `traceparent` header is present where they would normally start a transaction and propagate it.
 - MUST continue to support [log correlation](./log-correlation.md);
-- MUST NOT attempt to communicate with APM server, including central configuration;
-- MUST NOT log warnings/errors related to failures to communicate with APM server.
+- MUST NOT send event data to the APM server
 - SHOULD attempt to reduce runtime overhead where possible. For example,
   because events will be dropped there is no need to collect stack traces,
   collect metrics, calculate breakdown metrics, or to create spans (other than
   the top-level transaction required for context propagation, similarly to non-sampled traces).
 
+
 ### `disable_send` configuration
 
 Agents MAY implement this configuration option.