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

Annotations already establish read-only/idempotent behavior. The description adds useful context beyond annotations: no auth required, ODbL license, and the 50-object limit. It also states the return type (addresses and coordinates) without contradicting any annotation.

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?

Three compact sentences: what it does, when to use it, and legal/auth context. No redundant phrases; the most critical information is front-loaded.

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 a rich output schema and strong annotations, the description covers the essentials: purpose, usage context, constraint (max 50), auth, and licensing. Nothing needed for an agent to call it correctly 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?

Input schema covers 100% of the parameters with descriptions including the ID prefix format and max 50 limit. The description repeats the example and limit but adds no additional parameter semantics beyond the schema, so the baseline 3 is appropriate.

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?

Description states a specific verb ('look up'), resource ('OpenStreetMap objects by ID'), and output ('their addresses and coordinates'), with an ID format example. It is clearly distinct from the sibling nominatim.geocode.search (text-based) and nominatim.geocode.reverse (coordinate-based) tools.

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 a clear use case: 'resolving OSM IDs returned by other OSM-based tools.' This establishes when to use the tool, but it does not explicitly name alternative Nominatim tools or state when not to use them, which would warrant a 5.

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