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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is fully covered. Beyond that the description adds genuinely useful behavior: the dataset's coverage limits and the Polish-name-first matching with alias tolerance (Londyn and London both work). It says nothing about ranking, partial matches, or what happens when the query is ambiguous beyond the limit hint.

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?

Two tightly packed sentences with the output and scope front-loaded and the sibling routing second. Every clause carries information, though the parenthetical aside about Londyn makes the first sentence slightly dense.

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?

For a two-parameter lookup with a full output schema, the description covers nearly everything an agent needs: what is returned (lat, lon, tz), the dataset boundary, name tolerance, and downstream use. Return-value formatting is correctly left to the output schema.

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%, so the baseline is 3, and the description earns an extra point by clarifying that query accepts native Polish spellings and alternate names rather than only a canonical string. Limit semantics (how many candidates to return) remain documented only in the schema, not in the description.

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 names the exact resource and return payload (coordinates and IANA time zone of a town or city) and bounds coverage precisely: all Polish places plus world cities over 15,000. It also distinguishes the tool from its siblings by naming birth_chart and sky_at as consumers of the result.

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?

It gives concrete usage contexts: verifying which place birth_chart or sky_at will resolve to, and disambiguating multiple places with the same name before passing lat, lon and tz onward. It stops short of stating any when-not-to-use condition or what to do if zero results come back.

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