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

Annotations already declare readOnlyHint=true and destructiveHint=false, so safety is covered; the description goes further by disclosing the OAuth scope 'orders:read' and that the signed price_token is bound to catalog retail_eur, the same amount PRO credits debit. That is real behavioral context an agent cannot get from the structured fields, though it doesn't cover failure modes or what happens for non-PRO accounts beyond the credits hint.

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?

Four compact sentences, purpose front-loaded, with the ownership constraint and auth requirement following. No filler; every clause (no custom amount, price_token semantics, PRO checkout_mode, OAuth scope) carries information an agent needs.

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 structure needn't be spelled out, and the description still flags the salient returned fields (catalog_id, signed price_token, checkout_mode). Combined with the auth scope and ownership constraint, nothing an agent needs to call this correctly is missing.

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 meaning: 'titular-owned' narrows which ICCID is valid (ownership constraint not in the schema's 'original eSIM line'), and it ties price_token to retail_eur, clarifying what the currency parameter actually affects. The lang parameter is left to its enum-only schema description.

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 and resource ('List the exact doctorsim.com top-up packs') scoped to a titular-owned eSIM ICCID, which separates it from the generic plan-listing siblings like get_esim_plans and from the purchasing tool create_esim_topup. The '(same order as Mi Cuenta)' note pins down the exact catalog view the agent will get.

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 phrase 'No custom amount' implicitly excludes custom top-ups, and the ICCID requirement implies it is a pre-purchase lookup for an existing line. However, it never explicitly says when to use this instead of get_esim_plans, get_esim_plan_detail, or when to follow with create_esim_topup, so routing must be inferred.

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