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

With readOnlyHint/idempotent already declared, the description still adds substantial behavior: null means 'the site does not state it (never a no)', ratings only from 10+ reviews with source (Firmy.cz / Google Maps) and fetch date, IČO from the ČNB register, cross_border flag, and an explicit no-commission/no-affiliate/no-tracking stance. `filter_counts` and the 'unrated last' rule for the rating sort are also disclosed.

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?

Content largely earns its place, and the key caveat (not a ranking, no prices) is front-loaded. However, the body is one long run-on with deeply nested parentheticals, making it harder to parse than a few short sentences would be — density without structure.

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 does the heavy lifting by enumerating the returned card fields (kinds, products, online_kinds, assistance, app, claim form, registry, rating, tags, website). Minor gaps: `country` and `locale` behaviour and result volume/coverage are not addressed.

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; the description adds real meaning on top — sort ordering semantics (rating highest first, unrated last), the 2–3 id constraint for `compare`, and the kind/online/assistance/app/claim_online filter meanings. It does not clarify the `locale` parameter or repeat the enum tokens, but it goes beyond the schema in the areas that matter.

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 concrete verb and resource: answers the kinds of insurance for a country and returns `cards` with comparable non-price facts per insurer. It explicitly distances itself from price/ranking siblings (compare_energy, compare_mobile, find_best_price) with 'prices: false, ranking: false, score: null', so an agent can tell it apart without opening the 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?

Scope is implied (insurance in CZ) and the two modes — filtered list vs `compare` for 2–3 ids — are described, but there is no explicit 'use this when…' or 'do not use when…' guidance relative to the many compare_* siblings. The only directive given is a downstream instruction ('Tell the person to read the terms on the insurer's site'), not selection guidance.

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