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

Adds real context beyond the annotations: no credit consumption, authentication required even at zero credits, and the call still shares the account rate limit. It does not describe response size, ordering, or pagination, which matters for an unbounded list of countries and subdivisions.

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?

Front-loads the purpose, then the cost/auth constraints. Slight redundancy between 'Free of credit charges' and 'This call consumes no credits'—the same fact is stated twice, costing a sentence that does not earn its place.

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?

Covers the operational facts an agent needs to call it successfully: body format, authentication requirement, credit cost, and rate-limit sharing. With no output schema, it could still say something about the shape or size of the returned list, but nothing critical 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?

Zero parameters puts the baseline at 4, and the description correctly reinforces the schema's null shape by instructing the caller to send an empty JSON object, which is necessary given additionalProperties=false. No further parameter meaning exists to add.

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 ('Return every country and ISO 3166-2 administrative region known to the index'), which is clearly distinguishable from the singular-sounding sibling resolve_region. It stops short of naming siblings explicitly, so differentiation is implied rather than stated.

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 inferable from 'every ... region' (use this for the full catalogue rather than a single lookup), but the description never says when to prefer it over resolve_region or autocomplete. No exclusions or prerequisites are given beyond the empty-body instruction.

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