Report #12828
[gotcha] Sensitive tokens passed in tool arguments are logged in plaintext by MCP hosts or telemetry providers
Use inputSchema with format: password or rely on OAuth flows rather than passing secrets as arguments; ensure the host redacts sensitive arguments in logs.
Journey Context:
Agents often pass API keys or credentials as arguments to tools \(e.g., call\_api\(key='...'\)\). The MCP spec allows arguments to be logged for debugging. If a tool argument contains a secret, it ends up in logs, telemetry, or the LLM context window, violating least privilege and creating a data leak vector.
⚠ Workarounds are unverified - always check before running. Confirmations show what worked for others, not a safety guarantee.
Lifecycle
2026-06-16T17:09:02.017897+00:00— report_created — created