revert language in existing spec, update guidance to MUST for RFC3986 compliance

Author: evalstate

docs/specification/2025-03-26/server/resources.mdx

@@ -21,7 +21,7 @@ For example, applications could:
 - Allow the user to search through and filter available resources
 - Implement automatic context inclusion, based on heuristics or the AI model's selection
 
-![Example of resource context picker](resource-picker.png)
+![Example of resource context picker](/specification/2025-03-26/server/resource-picker.png)
 
 However, implementations are free to expose resources through any interface pattern that
 suits their needs—the protocol itself does not mandate any specific user
@@ -324,11 +324,6 @@ otherwise have a standard MIME type.
 
 Git version control integration.
 
-### Custom URI Schemes
-
-Custom URI schemes SHOULD be in accordance with [RFC3986](https://datatracker.ietf.org/doc/html/rfc3986),
-taking the above guidance in to account.
-
 ## Error Handling
 
 Servers **SHOULD** return standard JSON-RPC errors for common failure cases:

docs/specification/2025-03-26/server/tools.mdx

@@ -20,6 +20,7 @@ suits their needs—the protocol itself does not mandate any specific user
 interaction model.
 
 <Warning>
+
 For trust & safety and security, there **SHOULD** always
 be a human in the loop with the ability to deny tool invocations.
 
@@ -29,6 +30,7 @@ Applications **SHOULD**:
 - Insert clear visual indicators when tools are invoked
 - Present confirmation prompts to the user for operations, to ensure a human is in the
   loop
+
 </Warning>
 
 ## Capabilities
@@ -183,8 +185,12 @@ A tool definition includes:
 - `inputSchema`: JSON Schema defining expected parameters
 - `annotations`: optional properties describing tool behavior
 
-<Warning>For trust & safety and security, clients **MUST** consider
-tool annotations to be untrusted unless they come from trusted servers.</Warning>
+<Warning>
+
+For trust & safety and security, clients **MUST** consider
+tool annotations to be untrusted unless they come from trusted servers.
+
+</Warning>
 
 ### Tool Result
 
@@ -221,8 +227,8 @@ Tool results can contain multiple content items of different types:
 
 #### Embedded Resources
 
-[Resources](resources) **MAY** be embedded to provide additional context
-or data using a suitable [URI scheme](./resources#common-uri-schemes). Servers that use embedded resources **SHOULD** implement the `resources` capability:
+[Resources](/specification/2025-03-26/server/resources) **MAY** be embedded, to provide additional context
+or data, behind a URI that can be subscribed to or fetched again by the client later:
 
 ```json
 {

docs/specification/draft/server/resources.mdx

@@ -326,7 +326,7 @@ Git version control integration.
 
 ### Custom URI Schemes
 
-Custom URI schemes **SHOULD** be in accordance with [RFC3986](https://datatracker.ietf.org/doc/html/rfc3986),
+Custom URI schemes **MUST** be in accordance with [RFC3986](https://datatracker.ietf.org/doc/html/rfc3986),
 taking the above guidance in to account.
 
 ## Error Handling