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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and closed-world, so the safety profile is covered. The description adds the useful nuance that content is presented 'in the shop's own words' (i.e. shop-authored copy rather than neutral data), but says nothing about return format, freshness, or that results are localized by the bucket param.

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 front-loaded sentences with no filler; the topic list is dense but each item maps to a real question an agent might get. The enumeration is long but earns its place by signalling coverage boundaries.

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 read-only FAQ-style retrieval tool with no output schema and two optional, fully documented parameters, the description gives enough to know what content will come back and when to call it. Return shape and localization effects are the only remaining gaps.

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 description coverage is 100%, so baseline is 3. The description mentions no behaviour for bucket or language even though these control currency, locale and link language, so it adds no meaning beyond the schema.

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 a specific resource (shop facts) and enumerates the topical coverage: configurable eSIM, ranges, delivery, payment, hotspot, activation, top-ups, e-mails, support. It is distinguishable from the price-oriented siblings via the closing clause, though it does not name them directly.

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?

'Use for any question that is not a price' gives a clear use condition plus an explicit exclusion that routes pricing questions away from this tool. It stops short of naming the alternative tools (price_grid, quote_esim), which keeps it from a 5.

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