Get Marine Fuel Prices

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

Annotations already declare readOnlyHint and openWorldHint, so safety is covered. The description adds valuable context: it returns a table format, requires a Professional plan ($99/mo) or higher, and implies live/current pricing. No contradictions with annotations.

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 sentences: purpose, usage triggers, filter options, return format, and access requirement. Every sentence earns its place 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 low-complexity read-only tool with two optional params and no output schema, the description is complete. It covers purpose, filters, return type, and a critical access prerequisite (plan level), which is sufficient for selection and 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?

Schema coverage is 100% with both parameters already described. The description adds example port values and clarifies that filters can be used individually or together, but this is largely redundant with the schema, so it does not meaningfully extend the semantics beyond the baseline 3.

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 fetches latest marine fuel (bunker) prices for major shipping ports, with specific fuel types (VLSFO, MGO, IFO380) and port examples. This distinguishes it from siblings like opa_get_diesel_by_state or opa_get_fuel_surcharge.

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?

Explicitly says 'Use when the user asks about bunker fuel, marine fuel, VLSFO, MGO, IFO380, or shipping fuel costs,' giving clear trigger context. However, it does not explicitly name alternatives or state when not to use this tool, so it falls just short of a 5.

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