How to meet it
OWASP AISVS v1.01
Model Context Protocol (MCP) Security · Schema, Message, and Input Validation
Re-approve tools when their definition changes
Verify that MCP clients maintain a snapshot of tool definitions and that any change to a tool definition triggers re-approval before the modified tool can be invoked.
OWASP AISVS v1.01, requirement 10.4.8
In plain English
Keep a copy of approved tool definitions, and require approval again if a tool's definition changes.
What good looks like
- Approved definitions are stored.
- Changes are detected on each connection.
- Changed tools cannot be called until approved.
How teams usually do it
- Hashing tool definitions and comparing on connect.
Evidence an auditor would accept
- Client behaviour in a test where a definition changes.
Common mistakes
- Approving a server once and trusting all later tool changes.
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Requirement text from the OWASP AI Security Verification Standard, licensed under CC BY-SA 4.0. This guidance is shared under the same licence.