Build a client that learns supported operations instead of guessing.
1. Initialization
Establish the protocol version and supported capabilities before ordinary operations. Treat a failed handshake as an integration failure rather than sending speculative requests.
2. Tool discovery
Inspect tool names, descriptions and argument schemas. Validate the schema you support and apply an application allowlist; descriptions from a remote server are not trusted system instructions.
3. Changes and compatibility
Servers may change advertised capabilities. Handle missing or changed tools explicitly and test against a pinned server version for a reproducible release.
Worked scenario
A document server removes an export tool. The app disables export and explains the unavailable operation instead of hallucinating a successful result.
Apply it
Create a fake capability response and exercise supported, missing and malformed tools.
Check your understanding
Unknown capabilities produce a controlled result rather than arbitrary execution. Explain the decision and show evidence from your implementation or design. If you cannot demonstrate it yet, revisit the relevant section before continuing.