country_calling_codesLook up international calling (dialing) codes. With no args, lists all. Pass query to filter by country name, ISO code, or calling code (e.g. "germany", "DE", "49").
| Name | Required | Description | Default |
|---|---|---|---|
| query | No | Country name, ISO alpha-2 code, or calling code to search for. |
Changes observed during successful MCP inspections.
Input schema / examplesAdded value: +[
+ {
+ "query": "germany"
+ },
+ {
+ "query": "49"
+ }
+]Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare the tool as read-only, open-world, idempotent, and non-destructive. The description complements this by specifying that it returns a list of codes and that filtering is possible. It does not contradict annotations and adds value by describing the default behavior (listing all) and the type of filtering accepted.
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 extremely concise: two sentences that front-load the purpose and provide clear instructions. Every word serves a purpose, with no redundancy or extraneous information.
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 tool with one optional parameter and no output schema, the description is complete. It explains the tool's functionality, the effect of using vs. omitting the parameter, and gives examples. There is no missing information needed for an agent to use the tool 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 baseline is 3. The description adds examples ('germany', '49') and clarifies that the query parameter accepts country name, ISO code, or calling code. This reinforces the schema description and provides practical usage context, exceeding the bare minimum.
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 states the tool's purpose: looking up international calling codes. It specifies the behavior without arguments (lists all) and with a query (filters by country name, ISO code, or calling code), with concrete examples. This effectively distinguishes it from sibling tools, none of which serve the same function.
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 description provides explicit guidance on when to use the tool with or without the query argument. It explains that without arguments, it returns all codes, and with a query, it filters. While it does not compare to alternatives, the tool's narrow scope makes such comparison unnecessary. The guidance is clear and actionable.
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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