---
title: transforms
sidebarTitle: transforms
---

# `fastmcp.server.transforms`


Transform system for component transformations.

Transforms modify components (tools, resources, prompts). List operations use a pure
function pattern where transforms receive sequences and return transformed sequences.
Get operations use a middleware pattern with `call_next` to chain lookups.

Unlike middleware (which operates on requests), transforms are observable by the
system for task registration, tag filtering, and component introspection.

Example:
    ```python
    from fastmcp import FastMCP
    from fastmcp.server.transforms import Namespace

    server = FastMCP("Server")
    mount = server.mount(other_server)
    mount.add_transform(Namespace("api"))  # Tools become api_toolname
    ```


## Classes

### `GetToolNext` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/transforms/__init__.py#L36" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>


Protocol for get_tool call_next functions.


### `GetResourceNext` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/transforms/__init__.py#L44" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>


Protocol for get_resource call_next functions.


### `GetResourceTemplateNext` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/transforms/__init__.py#L52" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>


Protocol for get_resource_template call_next functions.


### `GetPromptNext` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/transforms/__init__.py#L60" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>


Protocol for get_prompt call_next functions.


### `Transform` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/transforms/__init__.py#L68" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>


Base class for component transformations.

List operations use a pure function pattern: transforms receive sequences
and return transformed sequences. Get operations use a middleware pattern
with `call_next` to chain lookups.


**Methods:**

#### `list_tools` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/transforms/__init__.py#L95" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
list_tools(self, tools: Sequence[Tool]) -> Sequence[Tool]
```

List tools with transformation applied.

**Args:**
- `tools`: Sequence of tools to transform.

**Returns:**
- Transformed sequence of tools.


#### `get_tool` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/transforms/__init__.py#L106" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
get_tool(self, name: str, call_next: GetToolNext) -> Tool | None
```

Get a tool by name.

**Args:**
- `name`: The requested tool name (may be transformed).
- `call_next`: Callable to get tool from downstream.
- `version`: Optional version filter to apply.

**Returns:**
- The tool if found, None otherwise.


#### `list_resources` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/transforms/__init__.py#L125" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
list_resources(self, resources: Sequence[Resource]) -> Sequence[Resource]
```

List resources with transformation applied.

**Args:**
- `resources`: Sequence of resources to transform.

**Returns:**
- Transformed sequence of resources.


#### `get_resource` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/transforms/__init__.py#L136" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
get_resource(self, uri: str, call_next: GetResourceNext) -> Resource | None
```

Get a resource by URI.

**Args:**
- `uri`: The requested resource URI (may be transformed).
- `call_next`: Callable to get resource from downstream.
- `version`: Optional version filter to apply.

**Returns:**
- The resource if found, None otherwise.


#### `list_resource_templates` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/transforms/__init__.py#L159" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
list_resource_templates(self, templates: Sequence[ResourceTemplate]) -> Sequence[ResourceTemplate]
```

List resource templates with transformation applied.

**Args:**
- `templates`: Sequence of resource templates to transform.

**Returns:**
- Transformed sequence of resource templates.


#### `get_resource_template` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/transforms/__init__.py#L172" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
get_resource_template(self, uri: str, call_next: GetResourceTemplateNext) -> ResourceTemplate | None
```

Get a resource template by URI.

**Args:**
- `uri`: The requested template URI (may be transformed).
- `call_next`: Callable to get template from downstream.
- `version`: Optional version filter to apply.

**Returns:**
- The resource template if found, None otherwise.


#### `list_prompts` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/transforms/__init__.py#L195" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
list_prompts(self, prompts: Sequence[Prompt]) -> Sequence[Prompt]
```

List prompts with transformation applied.

**Args:**
- `prompts`: Sequence of prompts to transform.

**Returns:**
- Transformed sequence of prompts.


#### `get_prompt` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/transforms/__init__.py#L206" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
get_prompt(self, name: str, call_next: GetPromptNext) -> Prompt | None
```

Get a prompt by name.

**Args:**
- `name`: The requested prompt name (may be transformed).
- `call_next`: Callable to get prompt from downstream.
- `version`: Optional version filter to apply.

**Returns:**
- The prompt if found, None otherwise.

