Get Marine Fuel Prices

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

Annotations already declare readOnlyHint and openWorldHint, and the description does not contradict them. It adds genuinely useful context beyond annotations: 'Requires an eligible account entitlement' flags an authorization precondition, and 'the API response is authoritative' warns the agent to trust the response over expectations. 'Returns available port prices' reinforces the open-world nature.

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?

Six sentences with the core purpose front-loaded in the first sentence. Each sentence earns its place: purpose, triggers, filters, return behavior, entitlement, and alternative routing. The filter sentence is slightly redundant with the schema but serves fast scanning.

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 tool (two optional string params, no output schema, no nested objects), the description covers purpose, usage triggers, parameter semantics, return scope, an entitlement prerequisite, and a routing alternative. Error behavior for missing entitlement or empty results is not described, but that is a minor gap given the tool's simplicity.

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 description coverage is 100%, so the schema fully documents both parameters. The description's filter sentence largely restates the schema, though 'and/or' does clarify that the two optional filters may be combined. This matches the baseline of 3 for high schema coverage with marginal added meaning.

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 states a specific verb and resource: 'Get latest marine fuel (bunker) prices returned for the account.' Naming VLSFO, MGO, and IFO380 anchors the domain precisely and differentiates it from siblings like opa_get_diesel_by_state or opa_get_price without needing to inspect their schemas.

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 trigger conditions are given ('Use when the user asks about bunker fuel, marine fuel, VLSFO, MGO, IFO380, or shipping fuel costs'), and an alternative is named with its condition: 'Use opa_get_plans for current access and pricing.' This gives the agent both a clear when-to-use and a clear when-not-to-use.

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