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

Beyond the annotations (readOnlyHint, openWorldHint, idempotentHint), the description discloses detailed output behavior: exact row shape, meaning of id as a slug that always refers to the current edition, the implication of labels:false on style.labels, and how layers relate to render_map. This gives agents actionable behavioral context not present in annotations.

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 dense but every sentence adds value: it starts with the core purpose, then explains row semantics, then query, then when to call. Advice like using common ids without listing is actionable. There is no filler and the structure front-loads the most important information.

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?

Given there is no output schema, the description fully compensates by specifying the output shape and the meaning of each field, including relationships to sibling tools and the practical consequence of labels:false. It also covers query behavior and fallback behavior for unknown ids, so an agent has everything needed to call and interpret the result.

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 already covers the single parameter (query) with a description identical to the one in the tool description, including the 'omit to list every map' behavior. With 100% schema coverage, the description adds no new meaning beyond repeating examples, so the baseline of 3 applies.

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: 'List the maps Ultimaps can render' and enumerates the kinds of maps (world, continents, countries subdivided into states, provinces, counties, departments, US ZIP areas). It also links the output to sibling tools ('id is the mapId for render_map and get_map_regions'), differentiating it as the catalog tool.

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?

Explicitly states when to call it: 'Only call this when you don't know the id' and gives concrete exceptions ('common ids such as world, united-states and europe just work'). It also explains how to narrow results with query, giving examples. This directly guides tool selection against siblings.

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