get_esim_planGet current details and an AeroCell checkout link for a plan ID from a single-country search. Requires the same country code.
| Name | Required | Description | Default |
|---|---|---|---|
| plan_id | Yes | Plan ID from a country search; requires the same country_code. | |
| country_code | Yes | Two-letter ISO country code, such as JP; XK is also supported by the catalog. |
| Name | Required | Description | Default |
|---|---|---|---|
| note | Yes | ||
| plan | Yes | ||
| country | Yes | ||
| currency | Yes | ||
| updated_at | Yes |
Changes observed during successful MCP inspections.
Input schema / additionalPropertiesRemoved value: -falseOutput schema / properties / plan / properties / includes_callsAdded value: +{
+ "type": "boolean"
+}Output schema / properties / plan / properties / includes_smsAdded value: +{
+ "type": "boolean"
+}Output schema / properties / plan / properties / provider_detailsAdded value: +{
+ "items": {
+ "additionalProperties": false,
+ "properties": {
+ "content": {
+ "type": "string"
+ },
+ "title": {
+ "type": "string"
+ }
+ },
+ "required": [
+ "title",
+ "content"
+ ],
+ "type": "object"
+ },
+ "type": "array"
+}Output schema / properties / plan / requiredPrevious value: -[
- "id",
- "name",
- "data_gb",
- "validity_days",
- "price_usd",
- "network",
- "operators",
- "covers_trip",
- "plan_page_url",
- "checkout_url"
-]New value: +[
+ "id",
+ "name",
+ "data_gb",
+ "validity_days",
+ "price_usd",
+ "network",
+ "operators",
+ "covers_trip",
+ "includes_calls",
+ "includes_sms",
+ "provider_details",
+ "plan_page_url",
+ "checkout_url"
+]Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
The annotations already establish that this is a read-only, non-destructive, open-world operation. The description adds that the result includes current details and a checkout link, but it does not disclose any further behavioral traits such as link expiration, authentication requirements, or error behavior when the country code mismatches.
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 description is two short sentences, front-loaded with the tool's core output and followed by the key usage constraint. There is no wasted language.
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 not be described. The description covers the essential retrieval scope and the country-code coupling; the main remaining gap is that it does not explicitly state whether regional plans are out of scope or what happens if the pair is mismatched.
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%, and both parameters are fully documented in the input schema. The description reinforces the coupling between plan_id and country_code, but this is already stated in the plan_id schema description, so it adds little beyond the structured fields.
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 specific verb and resource: get current details and an AeroCell checkout link for a plan ID. It also scopes the tool to plans from a single-country search, which implicitly distinguishes it from the broader sibling search tools, but it does not name those siblings explicitly.
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?
It gives clear context for use: the plan ID must come from a single-country search and the same country code is required. It does not explicitly name alternatives such as find_esim_plans or find_regional_esim_plans, but the single-country constraint provides a meaningful usage boundary.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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