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

Goes well beyond the readOnly/openWorld annotations: it warns that free callers are silently truncated to the first two areas, that dropped areas are surfaced in `locked`, and that null values/percentiles mean confidentiality suppression rather than zero. This is exactly the kind of hidden behavior an agent must know to interpret results correctly.

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-loads the purpose, then layers the truncation warning and null semantics efficiently. Slightly dense with several clauses, and the 'say so' instruction is response guidance rather than tool description, but every clause carries useful information.

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 no output schema, the description carries the return-value burden and does so: it explains `locked`, confidentiality nulls, paywalling, and the silent truncation. An agent has everything needed to call it and report results honestly.

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 real meaning: `places` accepts names or codes, and although the schema allows up to 12, the effective limit for free callers is two. The year-linked null semantics also enrich interpretation.

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 (side-by-side comparison) and resource (several Finnish postal areas' statistics), plus the added value (national benchmarks and percentiles). The multi-area framing distinguishes it from single-area siblings like get_area_report or get_place_stats.

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 comparison framing implies use when multiple areas must be viewed together, but no sibling is named and there is no explicit 'use this instead of X' or when-not guidance. The free-caller limit is disclosed, but that is behavioral rather than routing guidance.

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