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

Beyond the readOnlyHint and openWorldHint annotations, the description discloses source provenance (FRED/EIA), scope limits (up to 60 trading days, Cushing storage excluded), and pricing behavior ($0.002 USDC per successful call via x402, failed calls not charged). This is unusually complete behavioral context for invocation and cost awareness.

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?

Three compact sentences with no wasted words. The resource and units are front-loaded, followed by history scope, an exclusion, and payment terms, making it easy to parse quickly.

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 simple one-parameter read tool with an output schema and annotations already covering safety and openness, the description supplies all remaining essentials: source, units, scope, exclusion, and cost. Nothing material is missing for correct invocation.

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 schema already documents the single 'days' parameter with range and default, giving 100% schema description coverage. The description adds useful nuance by specifying 'trading days' and 'latest value plus up to 60 trading days of history', but it does not add further syntax or edge-case guidance beyond that.

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 names the exact resource (daily spot crude oil prices), the two benchmarks (WTI Cushing and Brent), units (USD per barrel), and source (FRED/EIA series). This clearly distinguishes it from sibling tools covering natural gas, weekly petroleum, OPEC monthly reports, and refined fuel bunkers.

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 clear context for using the tool: daily spot crude prices, latest value plus up to 60 trading days of history. It also includes an exclusion (Cushing storage levels are not included), which helps prevent misuse, but it does not explicitly name alternative sibling tools for related oil-market data.

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