Get Refining & Trading Spreads

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

Annotations already declare readOnlyHint and openWorldHint, so the safe, read-only nature is covered. The description adds valuable behavioral context by specifying the Professional plan ($99/mo) requirement and clarifying the semantics of 'basis' as regional price differentials, going beyond the schema.

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 short sentences efficiently cover purpose, usage triggers, and plan restriction. Each sentence adds distinct value with no redundancy or filler.

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 one-parameter tool with full schema coverage and safe annotations, the description is largely complete. It lacks explicit return format details, but this is not critical for a simple list-like lookup, and the openWorldHint annotation covers potential data variability.

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 'type' parameter with enum and descriptions, so the baseline is 3. The description enhances meaning by providing real-world equivalents like '3-2-1 crack' and refining margin proxy, which helps an agent map user intent to the correct enum value.

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's function with a specific verb and resource: 'Get refining and trading spreads'. It enumerates the three spread types (crack, basis, margin) and distinguishes itself from sibling price tools by focusing on spreads rather than absolute prices.

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?

Explicit usage guidance is provided: 'Use when the user asks about crack spreads, 3-2-1 crack, refining margins, basis differentials, or blend/transport margins.' This directly tells the agent when to select this tool over alternatives, and the plan requirement adds a clear prerequisite.

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