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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds valuable non-annotation context: the data source (UN/LOCODE via DataHub, not UNECE), the per-call price, the x402 payment rails, and the fact that failed calls are not charged.

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 front-loaded with the core lookup purpose, then appends two short sentences for data provenance and payment terms. Every sentence carries useful context for an agent deciding whether to invoke a paid, read-only lookup, and there is no redundant 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?

The tool is simple (one required parameter), has a full schema, an output schema, and annotations, so the description does not need to explain return values or safety. It adds the essential pricing and data-source details that are not in structured fields, though it leaves some sibling-selection context implicit.

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%, and the schema already defines the single parameter as a 5-letter UN/LOCODE with examples like FIHEL and SGSIN. The description repeats the same format and example but adds no further semantics such as case normalization or validation behavior, so the baseline of 3 is appropriate.

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: 'UN/LOCODE location lookup by 5-character code,' and enumerates returned attributes such as name, subdivision, status, port/rail/road/airport functions, IATA code, and coordinates. It is clear what the tool does, but it does not explicitly distinguish itself from siblings like logistics_airport_iata_icao or logistics_port_call_schedule.

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 implied by the need to look up a specific 5-character UN/LOCODE, but there is no explicit when-to-use/when-not guidance or named alternative tools. The payment note ('failed calls are not charged') is helpful context but does not clarify tool selection.

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