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

Annotations establish read-only, idempotent, open-world behavior; the description adds genuinely new operational context: result count cap (up to 5 hits), returned fields, a data-quality caveat (community map data, not a postal authority), and the full payment/auth model (x402 on Base, x-credit-token header, 1 free call/day, no API key).

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?

Front-loaded with the core address↔coordinates mapping and mode routing, then progressively adds output shape, data provenance, and pricing. Every sentence supplies information an agent needs to invoke the tool correctly; nothing is 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?

With an output schema present, return-value details are optional, yet the description still notes up to 5 hits with display name and address parts. Combined with the auth/pricing model and data caveat, an agent has everything needed to call this tool correctly.

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 description coverage is 100% and the schema already labels q as forward and lat/lon as reverse, so the description largely restates the same mapping (q= forward, lat=+lon= reverse). Baseline 3 is appropriate when the schema carries the parameter semantics.

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?

States a specific verb (geocode) plus the two modes (forward via q=, reverse via lat=+lon=) and the data source (OpenStreetMap Nominatim). An agent immediately understands the resource and how each parameter selects a mode, with no ambiguity against siblings like address_check or address_intel.

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 routes usage by parameter mode (forward vs reverse) and clarifies it is a geocoder rather than a postal-authority validator, implicitly steering away from address_trust/address_check. It does not, however, name any sibling tool as an alternative or state explicit when-not conditions.

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