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

Annotations already declare readOnlyHint=true and openWorldHint=false, but the description goes well beyond them: per-metric coverage windows (Paavo 2010–2024, housing prices 2009–2025, air quality from 2019 with sparse early stations) and the crucial semantic that an empty year list means unpublished, not zero. That last point prevents a real misinterpretation.

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 catalogue's contents, then routing, then the air-quality exception and the empty-list caveat. Every sentence carries information, though the long theme enumeration and the parenthetical air-quality code list make it denser than strictly necessary.

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?

There is no output schema, so the description has to describe returns itself — and it does: grouped by theme with codes, units and types, plus the alternate year-list shape and how to read an empty one. Nothing an agent needs 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?

Schema coverage is 100%, so baseline is 3, but the description adds genuine meaning: variableCode does not filter — it switches the tool into a different mode (years for that metric), and group is a case-insensitive theme filter. The coverage examples give the agent a sense of what values to expect. It stops short of enumerating valid group values.

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 — the catalogue of every metric Suomiatlas publishes — and enumerates the themes, codes, units and types it returns. It names the sibling tools it feeds (rank_areas, get_place_stats), so an agent can place it relative to the rest of the set without opening a schema.

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?

Explicitly says when to call it (to find the right variableCode for rank_areas or get_place_stats), what the alternative mode is (passing variableCode returns years instead of the catalogue), and carves out the air-quality codes that are NOT in this catalogue and must go straight to rank_areas. That is when/when-not/alternative routing in one place.

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