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fastmcp.utilities.auth

Authentication utility helpers.

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Functions

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decode_jwt_header 

decode_jwt_header(token: str) -> dict[str, Any]
Decode JWT header without signature verification. Useful for extracting the key ID (kid) for JWKS lookup. Args:
  • token: JWT token string (header.payload.signature)
Returns:
  • Decoded header as a dictionary
Raises:
  • ValueError: If token is not a valid JWT format

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decode_jwt_payload 

decode_jwt_payload(token: str) -> dict[str, Any]
Decode JWT payload without signature verification. Use only for tokens received directly from trusted sources (e.g., IdP token endpoints). Args:
  • token: JWT token string (header.payload.signature)
Returns:
  • Decoded payload as a dictionary
Raises:
  • ValueError: If token is not a valid JWT format

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parse_scopes 

parse_scopes(value: Any) -> list[str] | None
Parse scopes from environment variables or settings values. Accepts either a JSON array string, a comma- or space-separated string, a list of strings, or None. Returns a list of scopes or None if no value is provided.