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

Annotations already declare readOnlyHint=true and destructiveHint=false; the description reinforces this with 'Creates no order' and adds useful cross-tool context that the returned labels are the exact ones the pricing/order tools expect. It does not mention pagination or how live pricing is fetched, but against rich annotations the added context is solid.

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 tight sentences, front-loaded with the core resource and scope, with the sibling exclusion in a parenthetical and the safety note last. No filler.

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?

An output schema exists, so return values need no elaboration, and the description covers the key sibling routing plus required inputs implicitly. The only gap is the undocumented country_code, which neither schema nor description explains.

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 67%: the schema already documents coin (default USDC) and brand_slug's source. The description adds the semantic that coin selects live pricing, but leaves country_code entirely unexplained in both places. Baseline 3 is appropriate given the schema carries most of the load.

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 (List) and resource (a brand's live products/denominations with prices in a chosen coin), and explicitly carves out the eSIM case to sibling list_esim_plans. An agent can distinguish this from search_products/list_brands without reading further.

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?

Gives clear context: use it to get denomination labels that the pricing and order tools expect, and routes eSIM destinations elsewhere. However, it never states when NOT to use it beyond the eSIM exclusion, nor any prerequisite ordering against get_price/create_order.

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