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

Despite annotations already indicating read-only and idempotent, the description adds valuable behavior: country-specific backend selection, return of ranked suggestions with coordinates, and the 402 'upgrade_required' error handling. It also warns that NL and DE require a Starter+ subscription, which is crucial runtime context.

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, each dense with useful information: first sentence explains the mechanism, second lists return value and supported countries, third gives critical error handling. It is front-loaded with the core purpose and has no filler or redundant statements.

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, the description does not need to detail return fields, yet it still mentions ranked suggestions and coordinates. It covers the core functionality, all supported countries, and a key error scenario (402). The tool's complexity (multi-backend, country variations) is fully addressed in the description.

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?

The schema provides 100% coverage for parameters query and country, including descriptions and enum values. The description adds meaning beyond the schema by linking country codes to their authoritative registers and by highlighting the subscription limitation for NL and DE, which affects how the country parameter behaves.

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 clearly states it performs address autocomplete using authoritative registers and lists specific register names for countries (DAWA, Kartverket, BAN, MML, Nominatim). This distinguishes it from siblings like lookup_company or validate_vat, which serve different domains.

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 implies when to use (address suggestions) and gives concrete usage caveats: supported countries list, NL/DE subscription requirement, and explicit instruction 'do NOT retry on 402'. It lacks an explicit when-not-to-use statement, but the sibling tools are clearly in different domains, so the usage context is sufficient.

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