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

With no annotations, the description carries the full burden and does disclose meaningful traits: the third-party data source, the two return fields, an explicit error condition, and a quota/trial limit. It stops short of covering rate limiting beyond the trial, latency/availability of the upstream provider, or what an exhausted quota returns.

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 operation, followed by provider, return values, error behavior, and quota in a single compact sentence chain. Dense but well ordered; the emoji-prefixed pricing clause is the only soft addition.

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?

Return values are described, which matters since there is no output schema, and the error case is covered. But for a five-parameter tool with zero schema documentation and no annotations, the unresolved lat/lng/latitude/longitude alias situation leaves the agent guessing at the exact call shape.

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 0% across 5 parameters, so the description must compensate and only partially does. 'Missing lat or lon is a 400' signals that lat/lon are the operative names, but it is silent on lng, latitude, and longitude, which the schema offers as equally valid-looking properties with nothing marked required. An agent cannot tell from either source whether aliases are accepted, whether both coordinates are mandatory, or what string format (decimal degrees, negative values) is expected.

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 and resource ('Turn a coordinate into a human address'), names the underlying provider (OpenStreetMap Nominatim), and lists return fields. The direction of the transform (coordinate-input, address-output) implicitly separates it from the forward 'x402-geocode' sibling, though no sibling is named explicitly.

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?

Usage is implied by the input/output direction, and the description adds a useful operational constraint ('missing lat or lon is a 400') plus a pricing note ('5 free trial calls per signed wallet'). However, it never states when to prefer this over x402-geocode or x402-address-parse, nor what happens once the free calls are exhausted.

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