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

With no annotations provided, the description carries the full burden and excels. It discloses data-source behaviors (live market only during regular session, oracle frozen at close), the semantics of premiumPct versus driftPct, and the envelope's own clock for session verdict. This is rich, non-obvious behavioral context.

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 a compact paragraph of five sentences, each adding value: it introduces the three-way pricing, defines both metrics with caveats, and differentiates from siblings. No fluff; the most important facts are front-loaded.

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 absence of an output schema, the description effectively explains the return content: both metrics, the session verdict field, and the meaning of the values. It also provides enough context about data sources and timing to make the tool usable without further documentation.

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 zero parameters, so the baseline is 4 per rubric. The description adds no parameter information because none exists, but the input schema already confirms this. No deduction needed.

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 clearly states the tool returns pricing for tokenized stocks with three price sources (DEX, live market, oracle), and explains the key metrics premiumPct and driftPct. It explicitly differentiates from siblings by noting 'No other index on this chain has the live-market leg.'

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?

Provides explicit usage context: premiumPct is 'only meaningful while the session is open' and driftPct represents 'expected off-session drift, never an arbitrage claim.' This tells users when each metric is appropriate and warns against misinterpretation, while the sibling differentiation clarifies when to choose this tool.

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