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

Annotations already declare readOnlyHint=true, idempotentHint=true, openWorldHint=true, and destructiveHint=false, so the safety profile is covered. The description adds domain-specific behavior beyond annotations: NOI excludes non-operating items, the tool reports a single aggregate period, and default start/end dates are Jan 1 and Dec 31. It does not cover authentication or rate limits, but those are less critical for a read-only analytical tool.

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 front-loaded with the computation, followed by the critical usage restriction and alternative, then a compact parameter list. Every sentence adds necessary routing, scope, or parameter information without waste.

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?

Given the financial-analysis context, four parameters, 0% schema coverage, and an existing output schema, the description supplies everything needed to call correctly: the formula, single-period scope, sibling routing, mutual-exclusivity rule for portfolio vs property_ids, and date formats. Return values can remain in the output schema.

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?

With schema description coverage at 0%, the description fully compensates by explaining all four parameters: 'portfolio' as a named portfolio or 3-letter prefix, 'property_ids' as comma-separated IDs with an explicit 'Use this OR portfolio' rule, and both dates with MM/DD/YYYY format and their defaults.

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 and resource: 'Compute Net Operating Income (NOI) for a single period — Operating Income minus Operating Expenses, non-operating items excluded.' It also explicitly distinguishes itself from the closest sibling by naming analyze_pl_trend for general P&L/T12 requests.

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?

It gives explicit when-to-use guidance: 'Use this ONLY when the user specifically asks about NOI as a single aggregate number for a period.' It then names the alternative, analyze_pl_trend, and states the condition ('general P&L, Profit and Loss, or T12 request') that should route there instead.

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