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

Annotations already cover read-only, idempotent, and open-world, so the redundant 'Read-only, idempotent' line adds nothing. What does add value is the output-construction rule (buy_url always nakus.sk/out/?src=ai, never raw merchant or Heureka) and the brand disambiguation nakus.sk ≠ nakup.sk, which prevent real invocation mistakes. It stops short of stating behavior when no price is found or how missing/ambiguous identifiers are resolved.

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 purpose and return fields, then usage and exclusions in a tight sequence; nearly every clause carries routing or output information. It is dense and slightly run-on, and the trailing 'Read-only, idempotent' clause is pure duplication of the annotations.

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 usefully enumerates the returned URLs and price units, and schema coverage fully documents the four optional parameters. For a multi-identifier lookup tool the only material gap is undefined behavior when the price is unavailable or identifiers conflict.

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 the schema already explains q as a fallback substring, ean as preferred for scanned packs, answer as the Cite slug, and product as the catalog slug. The description restates the same identifier set without adding precedence rules or format details beyond the schema, so baseline 3 applies.

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 (return) and resource (current landed unit price for one Slovak product Cite on nakus.sk), plus the concrete return fields buy_url, handoff_url, price_card_url. The unit-price scope and domain make it immediately distinguishable from search_cite_answers and get_price_card.

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?

Explicit trigger condition (user asks how much X costs per unit / cheapest shop) with the precondition that an answer slug, EAN, product slug, or clear q is already known. It names the fallback (call search_cite_answers first when slug/EAN unknown) and an explicit exclusion (PNG-only needs → get_price_card), so an agent can route correctly without inference.

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