PrefectHQ · jlowin · Nov 1, 2025 · Nov 1, 2025 · Nov 1, 2025 · Nov 1, 2025
diff --git a/docs/changelog.mdx b/docs/changelog.mdx
@@ -1234,7 +1234,7 @@ This release introduces completely new tools for generating and customizing MCP
 
 ## [v2.4.0: Config and Conquer](https://github.com/jlowin/fastmcp/releases/tag/v2.4.0)
 
-**Note**: this release includes a backwards-incompatible change to how resources are prefixed when mounted in composed servers. However, it is only backwards-incompatible if users were running tests or manually loading resources by prefixed key; LLMs should not have any issue discovering the new route. See [Resource Prefix Formats](https://gofastmcp.com/servers/composition#resource-prefix-formats) for more.
+**Note**: this release includes a backwards-incompatible change to how resources are prefixed when mounted in composed servers. However, it is only backwards-incompatible if users were running tests or manually loading resources by prefixed key; LLMs should not have any issue discovering the new route.
 
 ### New Features 🎉
 

diff --git a/docs/servers/composition.mdx b/docs/servers/composition.mdx
@@ -41,7 +41,7 @@ FastMCP supports [MCP proxying](/servers/proxy), which allows you to mirror a lo
 
 You can also create proxies from configuration dictionaries that follow the MCPConfig schema, which is useful for quickly connecting to one or more remote servers. See the [Proxy Servers documentation](/servers/proxy#configuration-based-proxies) for details on configuration-based proxying. Note that MCPConfig follows an emerging standard and its format may evolve over time.
 
-Prefixing rules for tools, prompts, resources, and templates are identical across importing, mounting, and proxies.
+Prefixing rules for tools, prompts, resources, and templates are identical across importing, mounting, and proxies. When prefixes are used, resource URIs are prefixed using path format (since 2.4.0): `resource://prefix/path/to/resource`.
 
 ## Importing (Static Composition)
 
@@ -207,6 +207,10 @@ The same prefixing rules apply as with `import_server` for naming tools, resourc
     The `prefix` parameter is optional. If omitted, components are mounted without modification.
 </Tip>
 
+<Note>
+When mounting servers, custom HTTP routes defined with `@server.custom_route()` are also forwarded to the parent server, making them accessible through the parent's HTTP application.
+</Note>
+
 #### Performance Considerations
 
 Due to the "live link", operations like `list_tools()` on the parent server will be impacted by the speed of the slowest mounted server. In particular, HTTP-based mounted servers can introduce significant latency (300-400ms vs 1-2ms for local tools), and this slowdown affects the whole server, not just interactions with the HTTP-proxied tools. If performance is important, importing tools via [`import_server()`](#importing-static-composition) may be a more appropriate solution as it copies components once at startup rather than delegating requests at runtime.
@@ -320,62 +324,3 @@ This ensures that parent server tag policies act as a global policy for everythi
 <Note>
 This filtering applies to both **listing** (e.g., `list_tools()`) and **execution** (e.g., `call_tool()`). Filtered components are neither visible nor executable through the parent server.
 </Note>
-
-## Resource Prefix Formats
-
-<VersionBadge version="2.4.0" />
-
-When mounting or importing servers, resource URIs are usually prefixed to avoid naming conflicts. FastMCP supports two different formats for resource prefixes:
-
-### Path Format (Default)
-
-In path format, prefixes are added to the path component of the URI:
-
-```
-resource://prefix/path/to/resource
-```
-
-This is the default format since FastMCP 2.4. This format is recommended because it avoids issues with URI protocol restrictions (like underscores not being allowed in protocol names).
-
-### Protocol Format (Legacy)
-
-In protocol format, prefixes are added as part of the protocol:
-
-```
-prefix+resource://path/to/resource
-```
-
-This was the default format in FastMCP before 2.4. While still supported, it's not recommended for new code as it can cause problems with prefix names that aren't valid in URI protocols.
-
-### Configuring the Prefix Format
-
-You can configure the prefix format globally in code:
-
-```python
-import fastmcp
-fastmcp.settings.resource_prefix_format = "protocol" 
-```
-
-Or via environment variable:
-
-```bash
-FASTMCP_RESOURCE_PREFIX_FORMAT=protocol
-```
-
-Or per-server:
-
-```python
-from fastmcp import FastMCP
-
-# Create a server that uses legacy protocol format
-server = FastMCP("LegacyServer", resource_prefix_format="protocol")
-
-# Create a server that uses new path format
-server = FastMCP("NewServer", resource_prefix_format="path")
-```
-
-When mounting or importing servers, the prefix format of the parent server is used.
-
-<Note>
-When mounting servers, custom HTTP routes defined with `@server.custom_route()` are also forwarded to the parent server, making them accessible through the parent's HTTP application.
-</Note>
diff --git a/docs/servers/proxy.mdx b/docs/servers/proxy.mdx
@@ -266,8 +266,6 @@ These rules apply uniformly whether you:
 - Create a multi-server proxy from an `MCPConfig`
 - Use `FastMCP.as_proxy()` directly
 
-For resource URI prefix formats (path vs legacy protocol style) and configuration options, see Server Composition → Resource Prefix Formats.
-
 ## Mirrored Components
 
 <VersionBadge version="2.10.5" />

diff --git a/docs/servers/server.mdx b/docs/servers/server.mdx
@@ -357,15 +357,13 @@ import fastmcp
 # Access global settings
 print(fastmcp.settings.log_level)        # Default: "INFO"
 print(fastmcp.settings.mask_error_details)  # Default: False
-print(fastmcp.settings.resource_prefix_format)  # Default: "path"
 print(fastmcp.settings.strict_input_validation)  # Default: False
 print(fastmcp.settings.include_fastmcp_meta)   # Default: True
 ```
 
 Common global settings include:
 - **`log_level`**: Logging level ("DEBUG", "INFO", "WARNING", "ERROR", "CRITICAL"), set with `FASTMCP_LOG_LEVEL`
 - **`mask_error_details`**: Whether to hide detailed error information from clients, set with `FASTMCP_MASK_ERROR_DETAILS`
-- **`resource_prefix_format`**: How to format resource prefixes ("path" or "protocol"), set with `FASTMCP_RESOURCE_PREFIX_FORMAT`
 - **`strict_input_validation`**: Controls tool input validation mode (default: False for flexible coercion), set with `FASTMCP_STRICT_INPUT_VALIDATION`. See [Input Validation Modes](/servers/tools#input-validation-modes)
 - **`include_fastmcp_meta`**: Whether to include FastMCP metadata in component responses (default: True), set with `FASTMCP_INCLUDE_FASTMCP_META`
 - **`env_file`**: Path to the environment file to load settings from (default: ".env"), set with `FASTMCP_ENV_FILE`. Useful when your project uses a `.env` file with syntax incompatible with python-dotenv
@@ -399,7 +397,6 @@ Global FastMCP settings can be configured via environment variables (prefixed wi
 # Configure global FastMCP behavior
 export FASTMCP_LOG_LEVEL=DEBUG
 export FASTMCP_MASK_ERROR_DETAILS=True
-export FASTMCP_RESOURCE_PREFIX_FORMAT=protocol
 export FASTMCP_STRICT_INPUT_VALIDATION=False
 export FASTMCP_INCLUDE_FASTMCP_META=False
 ```

diff --git a/src/fastmcp/contrib/component_manager/component_service.py b/src/fastmcp/contrib/component_manager/component_service.py
@@ -105,16 +105,8 @@ async def _enable_resource(self, key: str) -> Resource | ResourceTemplate:
         # 2. Check mounted servers using the filtered protocol path.
         for mounted in reversed(self._server._mounted_servers):
             if mounted.prefix:
-                if has_resource_prefix(
-                    key,
-                    mounted.prefix,
-                    mounted.resource_prefix_format,
-                ):
-                    key = remove_resource_prefix(
-                        key,
-                        mounted.prefix,
-                        mounted.resource_prefix_format,
-                    )
+                if has_resource_prefix(key, mounted.prefix):
+                    key = remove_resource_prefix(key, mounted.prefix)
                     mounted_service = ComponentService(mounted.server)
                     mounted_resource: (
                         Resource | ResourceTemplate
@@ -148,16 +140,8 @@ async def _disable_resource(self, key: str) -> Resource | ResourceTemplate:
         # 2. Check mounted servers using the filtered protocol path.
         for mounted in reversed(self._server._mounted_servers):
             if mounted.prefix:
-                if has_resource_prefix(
-                    key,
-                    mounted.prefix,
-                    mounted.resource_prefix_format,
-                ):
-                    key = remove_resource_prefix(
-                        key,
-                        mounted.prefix,
-                        mounted.resource_prefix_format,
-                    )
+                if has_resource_prefix(key, mounted.prefix):
+                    key = remove_resource_prefix(key, mounted.prefix)
                     mounted_service = ComponentService(mounted.server)
                     mounted_resource: (
                         Resource | ResourceTemplate