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

Annotations already declare readOnlyHint, openWorldHint, and idempotentHint, so the description's job is lighter. It adds useful behavioral/contextual details: 'using OpenStreetMap data via Nominatim', 'No auth required', and the ODbL license with attribution to OpenStreetMap contributors. No contradictions with 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?

The description is three sentences, front-loaded with the primary action, then zoom scope, then auth/licensing. Every sentence adds a distinct piece of information, and there is no redundant wording.

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 tool's simplicity, 100% schema coverage, a rich output schema, and annotations that signal safe read-only idempotent behavior, the description covers purpose, zoom semantics, auth, and licensing. It doesn't mention rate limits or fallback behavior, but those are not critical for a basic reverse geocoder.

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%, and the schema already documents lat/lon ranges, zoom semantics (0=country, 10=city, 18=building), and language as an Accept-Language value. The description's 'from country down to individual building' is a paraphrase of the schema's zoom description rather than new information. Hence the baseline of 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?

The description opens with a specific verb ('Reverse geocode') and a clear resource ('latitude/longitude pair into the nearest address or place') while naming the data source (OpenStreetMap via Nominatim), which differentiates it from sibling reverse geocoders like address.geocodio.reverse. It clearly states the core function and distinguishes reverse from forward geocoding.

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 provides practical context such as 'No auth required' and explains the zoom scope, but it never names alternative tools or conditions for choosing this over address.geocodio.reverse or geo.address.reverse. Usage is implied rather than explicitly guided, leaving the agent to infer when Nominatim is the right choice.

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