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

Annotations already provide strong safety guarantees (readOnly, idempotent). The description adds context about the output being a polygon and the underlying service, but does not disclose limitations, rate limits, or behavior beyond that.

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 a single, front-loaded sentence that immediately states the purpose and key characteristics. It efficiently conveys the tool's output and source without unnecessary words.

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 the rich schema (full parameter descriptions, output schema exists) and strong annotations, the description is largely sufficient. It could benefit from a note about mutual exclusivity of time and distance or typical use cases, but overall it provides adequate context for an agent.

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 input schema has 100% description coverage for all parameters, including defaults, ranges, and mutual exclusivity. The tool description adds no additional parameter information beyond what the schema provides, so baseline score of 3 is appropriate.

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 specifies the tool retrieves a reachability area (isochrone) as a polygon from a point using time or distance. It includes the data source (Geoapify/OSM) and distinguishes it from siblings like route or place search by the unique concept of isochrone.

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?

The description implies usage for travel reachability analysis but does not explicitly state when to use this tool versus alternatives like routes or places. No guidance on choosing between time and distance parameters or when not to use it.

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