route_isochrone

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

Annotations already declare this as read-only, idempotent, and non-destructive, so the safety profile is covered. The description adds valuable behavioral context beyond annotations: it returns polygons, supports multiple travel modes, explains reverse catchment semantics, and notes that results can be passed directly to geom_relate or geom_overlay.

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 front-loaded with the core purpose, then organized into short paragraphs covering use cases, direction semantics, downstream composability, and the sibling alternative. Every sentence earns its place without unnecessary filler.

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 4-parameter tool with an output schema and strong annotations, the description covers everything an agent needs: what it does, when to use it, how direction affects results, what the output is, and how it can be consumed by other tools. Nothing important 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?

Schema coverage is 100%, so the baseline is 3, but the description adds meaning beyond the schema. It clarifies that profile corresponds to drive/walk/cycle time and gives practical guidance on when direction='to' is appropriate, which is more useful than the raw enum descriptions.

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 opens with a specific verb and resource: 'Map everywhere reachable within a travel-time budget.' It clearly distinguishes this tool from route_directions by stating that isochrones are for catchment and accessibility questions, not point-to-point paths.

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 names the use cases (catchment, accessibility, trade areas, coverage) and provides concrete examples. It also gives an exclusion rule: for a path to one specific destination, use route_directions instead, and explains when direction='to' is the correct choice.

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