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

Annotations already declare readOnly, idempotent, non-destructive and openWorld, so the safety profile is covered; the description adds genuinely new behavior: account entitlement is enforced by OilPriceAPI and no substitution is performed for missing quotes. It stops short of saying whether an unavailable quote yields an error or an omitted entry, and gives no rate-limit or cost information for an external paid API.

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?

Four short sentences, front-loaded with the core read operation and scope, then constraints. The grade enumeration partly duplicates the schema enum, but every sentence carries a distinct constraint (scope, preservation, no-substitution, entitlement) with no 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 two-parameter read tool with no output schema, the description covers scope, auth, entitlement and unavailability behavior, which is most of what an agent needs. It lacks return-shape hints and port-code guidance, but nothing essential for correct invocation is missing.

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 0%, so the description must carry the load, and it does: it enumerates the three valid grades, states that exactly one grade may be requested, and states the 1–2 port cardinality matching minItems/maxItems. It does not explain what the port codes (NLRTM, SGSIN, USHOU) represent or how to map a port name to a code, which is the main remaining gap.

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?

States a specific verb and resource ('Read authenticated bunker quotes') plus tight scope: 1–2 supported ports and one exact grade from an enumerated list. The marine-bunker framing is specific enough that an agent can distinguish it from generic price tools like energy_get_price or energy_get_latest without opening either schema.

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 constraints are implied rather than routed: it fixes the cardinality (1–2 ports, one exact grade) and forbids substitution when a quote is unavailable, which tells the agent how to call it. But it never says when to prefer this over siblings such as energy_get_price or energy_compare, nor does it state what to do when a port/grade pair is missing — the agent must infer error handling.

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