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fastmcp.utilities.storage

Key-value storage utilities for persistent data management.

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Classes

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KVStorage

Protocol for key-value storage of JSON data. Methods:

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get 

get(self, key: str) -> dict[str, Any] | None
Get a JSON dict by key.

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set 

set(self, key: str, value: dict[str, Any]) -> None
Store a JSON dict by key.

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delete 

delete(self, key: str) -> None
Delete a value by key.

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JSONFileStorage

File-based key-value storage for JSON data with automatic metadata tracking. Each key-value pair is stored as a separate JSON file on disk. Keys are sanitized to be filesystem-safe. The storage automatically wraps all data with metadata:
  • timestamp: Timestamp when the entry was last written
Args:
  • cache_dir: Directory for storing JSON files
Methods:

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get 

get(self, key: str) -> dict[str, Any] | None
Get a JSON dict from storage by key. Args:
  • key: The key to retrieve
Returns:
  • The stored dict or None if not found

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set 

set(self, key: str, value: dict[str, Any]) -> None
Store a JSON dict with metadata. Args:
  • key: The key to store under
  • value: The dict to store

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delete 

delete(self, key: str) -> None
Delete a value from storage. Args:
  • key: The key to delete

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cleanup_old_entries 

cleanup_old_entries(self, max_age_seconds: int = 30 * 24 * 60 * 60) -> int
Remove entries older than the specified age. Uses the timestamp field to determine age. Args:
  • max_age_seconds: Maximum age in seconds (default 30 days)
Returns:
  • Number of entries removed

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InMemoryStorage

In-memory key-value storage for JSON data. Simple dict-based storage that doesn’t persist across restarts. Useful for testing or environments where file storage isn’t available. Methods:

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get 

get(self, key: str) -> dict[str, Any] | None
Get a JSON dict from memory by key.

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set 

set(self, key: str, value: dict[str, Any]) -> None
Store a JSON dict in memory.

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delete 

delete(self, key: str) -> None
Delete a value from memory.