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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, openWorld), so the description's added value is the cost disclosure: 'A successful call consumes one account credit,' which also implies failed calls are free. It also tells the agent the response is shaped like the 'regions' listing entries, a useful behavioral detail not in any structured field.

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 tight sentences: purpose first, response shape second, cost third. Nothing is redundant and the most decision-relevant information is front-loaded.

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?

With no output schema, the description correctly points to the 'regions' entries for the return shape rather than leaving it undefined, and it discloses cost. It falls slightly short on the nested boundingBox case, which is the only structurally complex part of the input and goes unmentioned.

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 67% and the description says nothing about lat, lon, or boundingBox, so the schema carries the parameter burden. It never clarifies the relationship between the point parameters and the bounding-box object (precedence, mutual exclusivity, or what happens when all are omitted), which is the one semantic gap the schema does not close.

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: 'Resolve ISO 3166-2 administrative regions for coordinates,' which tells an agent exactly what it gets. It implicitly separates itself from the 'regions' sibling by referencing 'List regions' as the source of the entry shape, but it never distinguishes itself from 'reverse', which likely also accepts coordinates.

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 only implied by the phrase 'for coordinates' – there is no explicit statement of when to call this versus 'reverse' or 'regions'. No exclusions or prerequisites are given, leaving the agent to infer that this is the point-to-region lookup.

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