Tool Secrets
Tool secrets are sensitive values that are required to call a tool, such as API keys, passwords, and other credentials.
Tools MAY require secrets, as specified in the requirements.secrets field of the Tool Definition schema.
When a tool requires secrets, the client MUST retrieve the secrets (itself or via a trusted intermediary) and provide them in the Call Tool Request, before calling the tool.
If the client does not provide a secret in the Call Tool Request for a tool that requires a secret, the server MUST return a 400 Bad Request response as described in the Call Tool (Server Errors) section.