Why tool output needs validation
Model Context Protocol (MCP) connects applications and AI assistants to tools. A successful tool invocation does not guarantee the returned data is complete, current or safe to use. A tool can return a structurally valid transport message containing an invalid business payload.
Define the trusted boundary
Treat external tool results as untrusted input. Separate the MCP envelope from the application data inside it. Validate the JSON structure, confirm the expected source and tool identity, and apply authorization checks before the result influences a privileged action.
Create a contract for each critical tool
For a stock-check tool, require a product identifier, a nonnegative quantity and an observation timestamp. For a refund tool, require the original transaction identifier and a constrained currency code. Keep contracts narrow enough to catch errors but flexible enough to support planned changes.
Gate actions with explicit outcomes
An ALLOW result can permit the next deterministic step. A BLOCK result should prevent the action and surface a clear reason. A WARN result may allow read-only reasoning but should not automatically authorize a high-impact action. The application—not the model's wording—must enforce these policies.
Example agent workflow
The agent requests inventory, the integration parses the tool response, a validator checks it against the pinned contract, a freshness check evaluates the observation age, and a policy gate decides whether an order can proceed. If a check fails, the workflow requests a retry or human review instead of guessing.
Zorqelio integration note
Zorqelio offers JSON validation and monitored readiness decisions for agent workflows. Its MCP guide describes the available integration surface. It is a validation layer, not an agent runtime, and cannot independently establish whether a tool's factual claims are true.
For implementation details and current capabilities, consult the Zorqelio documentation. Technical examples are illustrative and should be tested against your own policies and supported schema dialect.