---
title: base
sidebarTitle: base
---
# `fastmcp.server.providers.base`
Base Provider class for dynamic MCP components.
This module provides the `Provider` abstraction for providing tools,
resources, and prompts dynamically at runtime.
Example:
```python
from fastmcp import FastMCP
from fastmcp.server.providers import Provider
from fastmcp.tools import Tool
class DatabaseProvider(Provider):
def __init__(self, db_url: str):
super().__init__()
self.db = Database(db_url)
async def list_tools(self) -> list[Tool]:
rows = await self.db.fetch("SELECT * FROM tools")
return [self._make_tool(row) for row in rows]
async def get_tool(self, name: str) -> Tool | None:
row = await self.db.fetchone("SELECT * FROM tools WHERE name = ?", name)
return self._make_tool(row) if row else None
mcp = FastMCP("Server", providers=[DatabaseProvider(db_url)])
```
## Classes
### `Provider`
Base class for dynamic component providers.
Subclass and override whichever methods you need. Default implementations
return empty lists / None, so you only need to implement what your provider
supports.
**Methods:**
#### `add_transform`
```python
add_transform(self, transform: Transform) -> None
```
Add a transform to this provider.
Transforms modify components (tools, resources, prompts) as they flow
through the provider. They're applied in order - first added is innermost.
**Args:**
- `transform`: The transform to add.
#### `list_tools`
```python
list_tools(self) -> Sequence[Tool]
```
Return all available tools.
Override to provide tools dynamically. Returns ALL versions of all tools.
The server handles deduplication to show one tool per name.
#### `get_tool`
```python
get_tool(self, name: str, version: VersionSpec | None = None) -> Tool | None
```
Get a specific tool by name.
Default implementation filters list_tools() and picks the highest version
that matches the spec.
**Args:**
- `name`: The tool name.
- `version`: Optional version filter. If None, returns highest version.
If specified, returns highest version matching the spec.
**Returns:**
- The Tool if found, or None to continue searching other providers.
#### `list_resources`
```python
list_resources(self) -> Sequence[Resource]
```
Return all available resources.
Override to provide resources dynamically. Returns ALL versions of all resources.
The server handles deduplication to show one resource per URI.
#### `get_resource`
```python
get_resource(self, uri: str, version: VersionSpec | None = None) -> Resource | None
```
Get a specific resource by URI.
Default implementation filters list_resources() and returns highest
version matching the spec.
**Args:**
- `uri`: The resource URI.
- `version`: Optional version filter. If None, returns highest version.
**Returns:**
- The Resource if found, or None to continue searching other providers.
#### `list_resource_templates`
```python
list_resource_templates(self) -> Sequence[ResourceTemplate]
```
Return all available resource templates.
Override to provide resource templates dynamically. Returns ALL versions.
The server handles deduplication.
#### `get_resource_template`
```python
get_resource_template(self, uri: str, version: VersionSpec | None = None) -> ResourceTemplate | None
```
Get a resource template that matches the given URI.
Default implementation lists all templates, finds those whose pattern
matches the URI, and returns the highest version matching the spec.
**Args:**
- `uri`: The URI to match against templates.
- `version`: Optional version filter. If None, returns highest version.
**Returns:**
- The ResourceTemplate if a matching one is found, or None to continue searching.
#### `list_prompts`
```python
list_prompts(self) -> Sequence[Prompt]
```
Return all available prompts.
Override to provide prompts dynamically. Returns ALL versions of all prompts.
The server handles deduplication to show one prompt per name.
#### `get_prompt`
```python
get_prompt(self, name: str, version: VersionSpec | None = None) -> Prompt | None
```
Get a specific prompt by name.
Default implementation filters list_prompts() and picks the highest version
matching the spec.
**Args:**
- `name`: The prompt name.
- `version`: Optional version filter. If None, returns highest version.
**Returns:**
- The Prompt if found, or None to continue searching other providers.
#### `get_tasks`
```python
get_tasks(self) -> Sequence[FastMCPComponent]
```
Return components that should be registered as background tasks.
Override to customize which components are task-eligible.
Default calls list_* methods, applies provider transforms, and filters
for components with task_config.mode != 'forbidden'.
Used by the server during startup to register functions with Docket.
#### `lifespan`
```python
lifespan(self) -> AsyncIterator[None]
```
User-overridable lifespan for custom setup and teardown.
Override this method to perform provider-specific initialization
like opening database connections, setting up external resources,
or other state management needed for the provider's lifetime.
The lifespan scope matches the server's lifespan - code before yield
runs at startup, code after yield runs at shutdown.
#### `enable`
```python
enable(self) -> None
```
Enable components by removing from blocklist, or set allowlist with only=True.
**Args:**
- `keys`: Keys to enable (e.g., "tool\:my_tool@" for unversioned, "tool\:my_tool@1.0" for versioned).
- `tags`: Tags to enable - components with these tags will be enabled.
- `only`: If True, switches to allowlist mode - ONLY show these keys/tags.
#### `disable`
```python
disable(self) -> None
```
Disable components by adding to the blocklist.
**Args:**
- `keys`: Keys to disable (e.g., "tool\:my_tool@" for unversioned, "tool\:my_tool@1.0" for versioned).
- `tags`: Tags to disable - components with these tags will be disabled.