Cheapest travel eSIM plans for a trip from every provider eSIMCompare tracks, plus a price index.
Scored across 3 tools
The three tools target distinct levels: provider-level comparison, country-level price index, and plan-level search. There is some overlap because compare_esim_providers mentions plans and prices while search_esim_plans returns plan pricing, but the descriptions make the different aggregation levels reasonably clear.
compare_esim_providers and search_esim_plans use a clear verb_noun pattern, while esim_price_index is a noun phrase. The deviation is minor and the names remain predictable and readable.
Three tools is on the lean side, but each covers a distinct and useful slice of the eSIM price comparison domain. No tool feels redundant, though the surface is small enough that users may want a few more entry points.
The set covers provider comparison, country-level pricing, and plan search, which are the core workflows for a travel eSIM price site. Minor gaps exist around listing supported destinations/providers explicitly or retrieving a specific plan's detail, but agents can generally work around these using the existing tools.
How travel eSIM providers stand against each other on eSIMCompare's data: plans and destinations covered, entry price, best price per GB, share of unlimited plans, an independent verdict, and links to the full review and head-to-head pages. Pass one to four providers, or none for all of them.
| Name | Required | Description | Default |
|---|---|---|---|
| providers | No | Provider names, such as ['Airalo', 'Holafly']. Omit for every provider. |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
The annotations already declare this as read-only, idempotent, non-destructive, and closed-world, so the safety profile is covered. The description adds valuable behavioral context by listing what the comparison returns: plans, destinations, pricing metrics, unlimited-plan share, verdict, and review links.
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?
The definition is two efficient sentences with no filler. It front-loads the comparison purpose and then states the provider-passing rule directly.
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 simple read-only comparison tool with one optional parameter and no output schema, the description provides enough detail about both the comparison dimensions and the returned information. Nothing critical is missing for an agent to select and call it correctly.
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 the single providers parameter is already well documented, including examples and omission behavior. The description adds cardinality and default behavior (one to four, or none for all), but mostly restates what the schema provides.
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 clearly frames the tool as a provider-vs-provider comparison and enumerates the dimensions compared, so the resource and operation are understandable. It does not explicitly contrast itself with siblings like search_esim_plans or esim_price_index, which keeps it from a 5.
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?
Usage is implied by the comparison framing, and the description gives practical input guidance: pass one to four providers or none at all. However, it does not state when to choose this tool over the sibling search or price-index tools, or when not to use it.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
What a week of mobile data costs a traveler: the cheapest eSIM with at least 5 GB valid for at least 7 days, per country, from eSIMCompare's price index of 194 countries. With a country: its price, the plan behind it, the cheapest price per GB, the cheapest unlimited week and its rank among all countries. Without one: the median, the cheapest and dearest countries, and which providers are cheapest most often.
| Name | Required | Description | Default |
|---|---|---|---|
| country | No | Country name or ISO code. Omit for the global summary. |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is fully covered. The description adds real context beyond that: the upstream source (eSIMCompare), the sample size (194 countries), and the exact plan thresholds used to compute the index. It does not disclose currency, data vintage, or behavior for an unmatched country name, which are meaningful for a price tool.
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 sentences, front-loaded with the metric definition before the mode-dependent return contents; nearly every clause carries information. The second sentence is a long comma-separated enumeration, but each item is a distinct output field rather than 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?
With no output schema, the description carries the burden of describing returns, and it does so for both branches (per-country plan, per-GB price, unlimited week, rank; global median, extremes, top providers). Gaps remain around currency/units, data recency, and unmatched-country behavior for a one-parameter tool that is otherwise simple.
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% and already defines the single country param, so the baseline is 3. The description adds value by explaining that the presence or absence of the parameter changes the entire result shape, not just a filter, which the schema only hints at with 'Omit for the global summary.'
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 states a precise, operationalized metric (cheapest eSIM with >=5 GB valid >=7 days) and its scope (per country, 194-country index), which is clearly distinct from the plan-level siblings compare_esim_providers and search_esim_plans. It never names those siblings, so the differentiation is inferable rather than stated.
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 with-country vs without-country split is spelled out with the exact payload each mode returns, which effectively tells the agent when to use each mode. It stops short of naming alternatives or exclusion conditions against the sibling tools.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Find the cheapest travel eSIM data plans for a destination from 16 providers (Airalo, Holafly, Nomad eSIM, Saily, Ubigi, Yesim and more), filtered to what a trip needs. Returns plans sorted by price (cheapest first) with data allowance, validity, price, price per GB, local network, speed policy, the date the price was checked, a page on eSIMCompare that cites the source, and a buy link. Buy links marked affiliate_link may earn eSIMCompare a commission; the price is the provider's own either way, and where a buy link applies a reader discount the plan also gives price_through_buy_url_usd.
| Name | Required | Description | Default |
|---|---|---|---|
| limit | No | How many plans to return (default 5). | |
| trip_days | No | Trip length in days: plans must stay valid at least this long. | |
| destination | Yes | Country or region, by name or ISO code: 'Japan', 'JP', 'United States', 'Europe', 'Global'. | |
| min_data_gb | No | Least data the trip needs, in GB. Unlimited plans always qualify. | |
| max_price_usd | No | Highest total price in US dollars. | |
| unlimited_only | No | Only unlimited-data plans. |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly/idempotent/non-destructive, and the description adds substantial context beyond them: result ordering (cheapest first), the full returned field list, the price-check date for freshness, affiliate disclosure with the reassurance that the price is the provider's own, and the price_through_buy_url_usd discount case. That is exactly the kind of trust and interpretation context an agent needs.
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 the core action and ordering, then the return fields, then disclosure. Every clause carries information, though the affiliate/discount explanation runs long relative to the rest and could be tightened without losing meaning.
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?
No output schema exists, and the description compensates by enumerating the returned fields (allowance, validity, price, price per GB, network, speed policy, checked date, citation page, buy link) and their semantics. Combined with 100% schema coverage on inputs and full annotation coverage on safety, an agent has everything needed to call and interpret this tool.
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 all six parameters are already documented, including the useful 'Unlimited plans always qualify' note for min_data_gb. The description adds no parameter-level syntax or format guidance beyond 'filtered to what a trip needs'; its added value is on the return side, not inputs, 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 and resource — 'Find the cheapest travel eSIM data plans for a destination' — plus coverage scope (16 named providers). It does not explicitly contrast itself with siblings compare_esim_providers and esim_price_index, so an agent must infer the distinction between searching plans versus comparing providers or reading an index.
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?
Usage is implied by the filter set ('filtered to what a trip needs' plus trip_days/min_data_gb/max_price_usd), so the agent can guess this is the retrieval tool for concrete plan options. However, no sentence states when to use this versus compare_esim_providers or esim_price_index, and there are no exclusions or prerequisites.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Recent tool additions, removals, and schema changes observed during successful MCP inspections.
compare_esim_providersesim_price_indexsearch_esim_plansCompare travel eSIM plans by country, days and data — live prices and links to buy on esimoa.
Neutral travel eSIM comparison: search and compare plans from many providers, ranked by price.
Compare prepaid travel eSIM plans by destination, data and trip length; plan multi-country trips.
Build-your-own travel eSIM: live quotes by country, GB, days and networks, plus a buy link.
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