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

Annotations already declare the operation read-only and open-world, so the safety profile is covered. The description adds that results are spatial and tied to coordinates, but omits result limits, pagination, or whether all modes are included by default.

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 definition is a single front-loaded sentence with no wasted clauses. It is appropriately brief for a simple lookup, though the absence of any second sentence leaves useful context unstated.

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 relatively simple spatial tool with annotations and no output schema, the description is minimally adequate. It implies the return type (stations and stops) but does not cover filtering behavior or practical limits, leaving some gaps for an agent invoking it.

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?

With only 50% schema description coverage and no parameter details in the description, the text mentions coordinates and a radius only conceptually. It does not explain the modes filter, radius defaults/bounds, or coordinate constraints, adding little beyond the schema.

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 clear resource (stations and stops) and spatial scope (within a radius of coordinates), which distinguishes it from generic stop lookups. It does not explicitly differentiate itself from sibling tools like find_stops, so it falls short of a 5.

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 parenthetical 'e.g. after geocoding an address' implies a common workflow, but the description never states when to use this tool versus find_stops or how it complements plan_journey. Usage context is only implied, not explicit.

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