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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the description is free to add the behavior that matters: free callers are benchmarked against a 12-week delayed reference value, and quote_date comparison is a paid-plan feature. That plan-gating and data-freshness disclosure is exactly the kind of context annotations cannot express.

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?

Two sentences, front-loaded with the user-facing question, then a single clause-rich sentence covering inputs, currency/unit flexibility, and each output. No filler or restatement of the title.

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?

There is no output schema, so the description must describe returns, and it does: difference %, verdict, range position, and overpayment. Combined with the plan-tier caveat and unit flexibility, an agent has everything needed to call and interpret this tool 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?

Schema coverage is 100%, so the baseline is 3, but the description goes further than the schema by explaining cross-parameter semantics: unit accepts any measure and defaults to the benchmark's unit, and supplying quantity is what triggers the overpayment calculation. Those are behavioral linkages between parameters that the schema alone does not convey.

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 opens with the exact question the tool answers and then enumerates the concrete outputs: difference %, FAIR/HIGH/LOW verdict, position in the benchmark's 12-month range, and overpayment. This is a specific verb+resource statement that an agent can distinguish from sibling pricing tools like estimate_packaging_price or packiq_quote_analysis.

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 framing question ('Is this supplier price fair?') makes the trigger condition obvious: you have a quoted supplier price and want it evaluated against a benchmark. However, it never names an alternative tool or states when not to use it, so sibling routing (e.g. versus packiq_quote_analysis or get_live_index) is left to inference.

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