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

Annotations cover the safety profile (readOnlyHint, openWorldHint), so the bar is lower, and the description adds real behavioral value: the response identifies the Guides city and out-of-city coordinates yield an empty list. It doesn't discuss pagination or result size, but the edge-case disclosure is meaningful context beyond the 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?

Three tight sentences, front-loaded with the core action and scope, followed by the edge case and then the sibling routing. No sentence is wasted.

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 annotations and an output schema already present, the description is largely complete: it covers purpose, scoping, edge case, and alternatives. Only minor behavioral details like pagination are absent, which is acceptable given the output schema.

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 100%, so the schema already documents latitude, longitude, span, lang, and country. The description only restates that span sets the area, adding no syntax or format detail beyond the schema, so the baseline 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?

States a specific verb (Fetch) and resource (Apple Guide summary items) with explicit geographic scoping via latitude/longitude/span. It clearly distinguishes itself from the guide-detail and search siblings by describing the 'nearby/curated around coordinates' behavior.

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 routes the agent to three named alternatives with the condition that selects each: apple_maps_guides_cities for supported cities, apple_maps_guides_lookup for name search, apple_maps_guide for a single guide. It also states the edge case that coordinates outside a Guides city return an empty list.

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