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

The description discloses significant behavioral details beyond the annotations, including that regime=null for most cities, the distinction between actual reduction and note-only regimes, and that reduction_pct and flat_rate are null for note-only regimes. It also states the tool is read-only with no side effects, and explains the return format (text summary plus structured JSON). This exceeds what annotations alone provide.

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 long but every sentence contributes essential information: the core purpose, null semantics, country coverage, regime types, and return content. It is front-loaded with the main action and progresses logically without redundancy, making it appropriately sized for the tool's complexity.

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 complexity, the description thoroughly covers edge cases and return values, explaining null behavior, note-only regimes, what fields are null, and what each entry contains. With an output schema present, the description still adds necessary context about the tool's limitations and eligibility conditions not tested, making it complete for correct selection and invocation.

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% for the single city parameter, so the baseline is 3. The description does not add additional semantics beyond the schema; it only reiterates that the tool looks up a city. The schema already provides the city slug hint and the reference to list_cities, so the description adds minimal parameter-level value.

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 the tool looks up a city's inbound-worker tax regime, using the verb 'look up' and specifying the resource. It distinguishes from siblings by noting it surfaces special reduced-tax schemes that general cost-of-living tools do not, which differentiates it from get_city_summary or get_safety_net.

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 clear context for when to use the tool: when you need a city's inbound-worker tax regime, especially the special reduced-tax schemes not covered by general cost-of-living tools. It also notes that most cities return null, implying this tool will often yield no data, but it does not explicitly name alternative sibling tools or state when not to use it.

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