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

Beyond the annotations (readOnlyHint, openWorldHint, idempotentHint), the description adds significant behavioral context: it mentions population filtering, sorting modes, layer filtering, and even warns that larger radii return 400 INVALID_QUERY. This extra detail about error conditions and customization goes beyond what annotations provide.

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 concise (3 sentences) and front-loaded with the primary purpose. It packs in usage guidance, feature highlights, and an alternative tool without unnecessary filler. Every sentence contributes meaning.

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?

For a tool with 9 parameters, an output schema, and a rich set of features, the description is remarkably complete. It covers the core purpose, when to use it, key capabilities, limitations (radius error), and alternatives. The output schema exists, so return values need not be described. This is a fully self-sufficient description.

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 documents all 9 parameters with descriptions (100% coverage), so the baseline is 3. The description adds functional context by explaining how parameters like population filtering, sorting, and layers work together (e.g., 'cities > 100k' implies min_population). This adds value beyond the schema, hence a 4.

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 clearly identifies the tool as a browsing/discovery search for cities, neighbourhoods, or mixed venues near a location. It distinguishes itself from sibling tools by explicitly stating it is for exploring a region rather than a specific category, and names search_places as the alternative for specific POI categories.

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 provides explicit guidance on when to use this tool ('when the user is exploring a REGION rather than looking for a specific category') and names an alternative tool (search_places) for different use cases. This is clear, actionable guidance.

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