Which boundaries a map can draw, and how its regions are named

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

Annotations already declare readOnlyHint=true and idempotentHint=true, so the safety profile is covered. The description adds the key behavioral detail that 'unknown regions fail loudly', which is not in annotations, and it advises reading the list before naming regions to avoid such failures. This enriches the agent's understanding of the tool's behavior beyond the structured metadata.

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 compact and front-loaded: the first clause states the main scope and format. It packs useful guidance (id usage, error behavior, chart setup) into two sentences without redundancy. The density is high but every phrase earns its place; it could be slightly clearer with sentence breaks but remains efficient.

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?

There is no output schema, so the description must explain what the tool returns—it does ('full region list — codes (ISO 3166-2 like DE-BY), names and aliases'). It also covers error behavior, usage patterns (setting chart.geography), and the purpose (region naming validation). For a list/retrieval tool with one optional parameter, nothing an agent needs 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?

The schema description for 'id' is already explicit (provides example 'de-regions' and explains omission). The description adds further semantic value by explaining the id format convention (alpha-2 like de-regions), the nature of the output (ISO 3166-2 codes like DE-BY, names, aliases), and the importance of checking it. This goes beyond the schema's basic parameter documentation.

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 ('list') and resource ('geographies'), then enumerates the scopes (countries, us-states, country states/provinces) and the output format (alpha-2 regions). It clearly differentiates from sibling tools like list_assets or list_brands by its unique domain, leaving no ambiguity about what it does.

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?

It explicitly explains when to pass the optional id ('Pass id to get one geography's full region list') and when to omit it ('omit to list all'). It also gives a strong usage directive: 'read it BEFORE naming regions in your data' and warns about failure behavior, which effectively tells the agent the right time and reason to invoke this tool.

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