Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

The annotations already provide readOnlyHint, idempotentHint, and destructiveHint, and the description adds value by clarifying the read-only behavior ('Cannot spend money') and by disclosing a potential pitfall: scan_age_ms is included so stale verdicts are not mistaken for fresh ones. This is meaningful behavioral context beyond the structured annotations.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is well-structured and front-loaded with the primary use case. Minor redundancy exists: 'Read-only' and 'Cannot spend money' say the same thing and are also covered by annotations, so a small amount of trimming could tighten it further.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a zero-parameter read-only inventory tool with no output schema, the description is sufficiently complete. It states the exact data scope, the freshness guard (scan_age_ms), the non-spending guarantee, and the appropriate trigger questions. An agent has everything needed to call it correctly.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The tool has 0 parameters, so the baseline is 4. The description adds no parameter-specific detail because none is needed; it instead clarifies what the returned inventory will contain, which is more relevant for a no-argument list tool.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description states a specific verb ('List'), an explicit resource ('the user's domain inventory'), and enumerates the returned data (verification challenge status, cached liveness, classification, title, expiry). This clearly distinguishes it from siblings like check_live or verify_ownership by framing it as the inventory overview tool.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description gives explicit usage contexts: start of portfolio, renewal, and 'what do I own' questions, and tells the agent to use it before suggesting a purchase. It does not explicitly name alternative tools or state when not to use it, but the situational guidance is clear enough to route correct invocation.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.