> ## Documentation Index
> Fetch the complete documentation index at: https://gofastmcp.com/llms.txt
> Use this file to discover all available pages before exploring further.
# versions
# `fastmcp.utilities.versions`
Version comparison utilities for component versioning.
This module provides utilities for comparing component versions. Versions are
strings that are first attempted to be parsed as PEP 440 versions (using the
`packaging` library), falling back to lexicographic string comparison.
Examples:
* "1", "2", "10" → parsed as PEP 440, compared semantically (1 \< 2 \< 10)
* "1.0", "2.0" → parsed as PEP 440
* "v1.0" → 'v' prefix stripped, parsed as "1.0"
* "2025-01-15" → not valid PEP 440, compared as strings
* None → sorts lowest (unversioned components)
## Functions
### `parse_version_key`
```python theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}}
parse_version_key(version: str | None) -> VersionKey
```
Parse a version string into a sortable key.
**Args:**
* `version`: The version string, or None for unversioned.
**Returns:**
* A VersionKey suitable for sorting.
### `version_sort_key`
```python theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}}
version_sort_key(component: FastMCPComponent) -> VersionKey
```
Get a sort key for a component based on its version.
Use with sorted() or max() to order components by version.
**Args:**
* `component`: The component to get a sort key for.
**Returns:**
* A sortable VersionKey.
### `compare_versions`
```python theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}}
compare_versions(a: str | None, b: str | None) -> int
```
Compare two version strings.
**Args:**
* `a`: First version string (or None).
* `b`: Second version string (or None).
**Returns:**
* -1 if a \< b, 0 if a == b, 1 if a > b.
### `is_version_greater`
```python theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}}
is_version_greater(a: str | None, b: str | None) -> bool
```
Check if version a is greater than version b.
**Args:**
* `a`: First version string (or None).
* `b`: Second version string (or None).
**Returns:**
* True if a > b, False otherwise.
### `max_version`
```python theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}}
max_version(a: str | None, b: str | None) -> str | None
```
Return the greater of two versions.
**Args:**
* `a`: First version string (or None).
* `b`: Second version string (or None).
**Returns:**
* The greater version, or None if both are None.
### `min_version`
```python theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}}
min_version(a: str | None, b: str | None) -> str | None
```
Return the lesser of two versions.
**Args:**
* `a`: First version string (or None).
* `b`: Second version string (or None).
**Returns:**
* The lesser version, or None if both are None.
### `dedupe_with_versions`
```python theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}}
dedupe_with_versions(components: Sequence[C], key_fn: Callable[[C], str]) -> list[C]
```
Deduplicate components by key, keeping highest version.
Groups components by key, selects the highest version from each group,
and injects available versions into meta if any component is versioned.
**Args:**
* `components`: Sequence of components to deduplicate.
* `key_fn`: Function to extract the grouping key from a component.
**Returns:**
* Deduplicated list with versions injected into meta.
## Classes
### `VersionSpec`
Specification for filtering components by version.
Used by transforms and providers to filter components to a specific
version or version range. Unversioned components (version=None) always
match any spec.
**Args:**
* `gte`: If set, only versions >= this value match.
* `lt`: If set, only versions \< this value match.
* `eq`: If set, only this exact version matches (gte/lt ignored).
**Methods:**
#### `matches`
```python theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}}
matches(self, version: str | None) -> bool
```
Check if a version matches this spec.
**Args:**
* `version`: The version to check, or None for unversioned.
* `match_none`: Whether unversioned (None) components match. Defaults to True
for backward compatibility with retrieval operations. Set to False
when filtering (e.g., enable/disable) to exclude unversioned components
from version-specific rules.
**Returns:**
* True if the version matches the spec.
#### `intersect`
```python theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}}
intersect(self, other: VersionSpec | None) -> VersionSpec
```
Return a spec that satisfies both this spec and other.
Used by transforms to combine caller constraints with filter constraints.
For example, if a VersionFilter has lt="3.0" and caller requests eq="1.0",
the intersection validates "1.0" is in range and returns the exact spec.
**Args:**
* `other`: Another spec to intersect with, or None.
**Returns:**
* A VersionSpec that matches only versions satisfying both specs.
### `VersionKey`
A comparable version key that handles None, PEP 440 versions, and strings.
Comparison order:
1. None (unversioned) sorts lowest
2. PEP 440 versions sort by semantic version order
3. Invalid versions (strings) sort lexicographically
4. When comparing PEP 440 vs string, PEP 440 comes first