SmartVerify glossary

MCP tool-call refusal

Definition

MCP tool-call refusal is a request-path control that stops a Model Context Protocol tool call before the tool server acts on it and returns a typed error to the agent framework.

Scope

The decision applies to an MCP or JSON-RPC tool call observed on the customer network path. When refused, the call is not forwarded, so the tool has no partial effect and there is nothing to roll back. This control is separate from refusing a PostgreSQL statement on the database path.

Examples

  • Refuse a call to a tool the agent is not permitted to invoke.
  • Refuse a call whose arguments violate an approved rule before it reaches the tool server.
  • Return a typed tool error that the agent framework can handle instead of forwarding the blocked call.

Current availability

Available now

MCP and JSON-RPC observation and tool-call refusal are available now when the tool-server connection passes through the customer network path. Individual PostgreSQL statement refusal by kind, target table, column, or value is a separate control in design partner build. The Platform coverage grid is the source of truth for availability.

Related technical detail: Platform coverage grid.