Retrieve Japanese address information from a postal code. Provide a code like 1000001 or 100-0001 to get the corresponding address details.
Look up address information from a Japanese postal code
| Name | Required | Description | Default |
|---|---|---|---|
| postalCode | Yes | Japanese postal code (e.g., '1000001' or '100-0001') |
Changes observed during successful MCP inspections.
v0.1.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description carries the burden of behavioral disclosure. It implies a read-only lookup, but does not state that it is non-mutating, does not mention rate limits, caching, or error behavior for invalid codes. The address-information framing adds some useful domain context.
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?
A single efficient sentence that front-loads the action and resource. No unnecessary words, though it could be slightly more informative about the lookup scope.
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 one-parameter read tool, the description is adequate but thin. With no output schema and no annotations, it leaves the return shape and behavioral expectations (e.g., what address fields are returned, what happens on invalid input) unaddressed.
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 documents the postalCode format with examples. The description adds nothing beyond what the schema provides, so the baseline 3 is appropriate.
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 (look up) and resource (address information) scoped to Japanese postal codes, so the purpose is clear. It is distinguished from search_address by the postal-code input, though the sibling relationship is not made explicit.
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 input constraint (Japanese postal code) hints at when to use this tool, but there is no explicit guidance on when to prefer it over search_address or when not to use it. The sibling tool is named but not referenced.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.