---
title: components
sidebarTitle: components
---

# `fastmcp.utilities.components`

## Functions

### `get_fastmcp_metadata` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/components.py#L26" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
get_fastmcp_metadata(meta: dict[str, Any] | None) -> FastMCPMeta
```


Extract FastMCP metadata from a component's meta dict.

Handles both the current `fastmcp` namespace and the legacy `_fastmcp`
namespace for compatibility with older FastMCP servers.


## Classes

### `FastMCPMeta` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/components.py#L20" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

### `FastMCPComponent` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/components.py#L74" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>


Base class for FastMCP tools, prompts, resources, and resource templates.


**Methods:**

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

```python
make_key(cls, identifier: str) -> str
```

Construct the lookup key for this component type.

**Args:**
- `identifier`: The raw identifier (name for tools/prompts, uri for resources)

**Returns:**
- A prefixed key like "tool:name" or "resource:uri"


#### `key` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/components.py#L139" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
key(self) -> str
```

The globally unique lookup key for this component.

Format: "{key_prefix}:{identifier}@{version}" or "{key_prefix}:{identifier}@"
e.g. "tool:my_tool@v2", "tool:my_tool@", "resource:file://x.txt@"

The @ suffix is ALWAYS present to enable unambiguous parsing of keys
(URIs may contain @ characters, so we always include the delimiter).

Subclasses should override this to use their specific identifier.
Base implementation uses name.

Prefer `.key` over ad-hoc `name or uri or uri_template` logic for any
cross-component identity work (dedupe, grouping, collision detection,
lookup tables). It encodes type, identifier, and version, so variants
of the same component don't falsely collide with each other, and
cross-type identifiers (e.g. a tool and a resource both named "foo")
can't clash.


#### `get_meta` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/components.py#L161" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
get_meta(self) -> dict[str, Any]
```

Get the meta information about the component.

Returns a dict that always includes a `fastmcp` key containing:
- `tags`: sorted list of component tags
- `version`: component version (only if set)

Internal keys (prefixed with `_`) are stripped from the fastmcp namespace.


#### `enable` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/components.py#L209" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
enable(self) -> None
```

Removed in 3.0. Use server.enable(keys=[...]) instead.


#### `disable` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/components.py#L216" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
disable(self) -> None
```

Removed in 3.0. Use server.disable(keys=[...]) instead.


#### `copy` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/components.py#L223" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
copy(self) -> Self
```

Create a copy of the component.


#### `register_with_docket` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/components.py#L227" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
register_with_docket(self, docket: Docket) -> None
```

Register this component with docket for background execution.

No-ops if task_config.mode is "forbidden". Subclasses override to
register their callable (self.run, self.read, self.render, or self.fn).


#### `coerce_task_arguments` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/components.py#L235" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
coerce_task_arguments(self, arguments: dict[str, Any]) -> dict[str, Any]
```

Validate and coerce task arguments before any task state is created.

Called by ``submit_to_docket`` up front, so invalid inputs raise before
the task's Redis metadata and initial status notification exist —
otherwise a coercion failure during queueing would orphan a task the
client has already observed. The base implementation is a no-op;
components that splat arguments into a typed Python callable (e.g.
``FunctionTool``) override this to mirror the synchronous validation
path.


#### `add_to_docket` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/components.py#L248" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
add_to_docket(self, docket: Docket, *args: Any, **kwargs: Any) -> Execution
```

Schedule this component for background execution via docket.

Subclasses override this to handle their specific calling conventions:
- Tool: add_to_docket(docket, arguments: dict, **kwargs)
- Resource: add_to_docket(docket, **kwargs)
- ResourceTemplate: add_to_docket(docket, params: dict, **kwargs)
- Prompt: add_to_docket(docket, arguments: dict | None, **kwargs)

The **kwargs are passed through to docket.add() (e.g., key=task_key).


#### `get_span_attributes` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/components.py#L270" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
get_span_attributes(self) -> dict[str, Any]
```

Return span attributes for telemetry.

Subclasses should call super() and merge their specific attributes.

