Multi-Commodity Market Brief

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

Annotations declare readOnlyHint and openWorldHint, but the description adds substantial behavioral context: it reveals the API key requirement (OILPRICEAPI_KEY), that the call counts as 1 request, and that per-tier code limits apply (free: 3 codes). It also discloses the narrative option's added content, going well beyond the annotations without contradicting them.

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 four sentences, each earning its place: core purpose, use cases, param behavior, and auth/limits/alternatives. It is front-loaded with the most important information and contains no fluff or repetition of structured fields.

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?

Despite lacking an output schema, the description clearly enumerates what the tool returns (spot prices, 24h changes, forecasts, spreads, optional narrative context) and covers resource constraints (API key, request count, tier limits). For a two-parameter read-only tool, this is comprehensively sufficient.

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% and both parameters are described, but the description adds meaningful nuance: it explicitly states that codes accept natural language ('brent', 'us gas') or API codes, and clarifies that narrative adds a 'plain-English summary plus market context.' This exceeds the schema's basic parameter documentation, earning a score above the baseline.

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 a specific verb and resource: 'Get a multi-commodity market brief' with concrete contents (spot prices, 24h changes, 1-month forecasts, spreads). It clearly distinguishes this from sibling tools by emphasizing 'several commodities in ONE call' and explicitly contrasts with single-price and subscription tools.

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?

Usage is explicitly stated: 'Use when the user wants a market snapshot, morning brief, or an at-a-glance read across multiple commodities.' It also names two alternatives with clear disambiguation: 'For a single price use opa_get_price; for ongoing recurring monitoring use opa_create_price_subscription.' This is exemplary guidance.

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