Find Japanese postal codes by entering an address query. Filter results by prefecture or city to quickly resolve addresses into postal codes.
Search for postal codes by address
| Name | Required | Description | Default |
|---|---|---|---|
| city | No | City name to filter results | |
| query | Yes | Address query in Japanese | |
| prefecture | No | Prefecture name to filter results |
Changes observed during successful MCP inspections.
v0.1.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations provided, the description carries the full behavioral burden. It implies a read-only search but says nothing about result limits, matching behavior, or whether the query is fuzzy/partial. For a lookup tool this is a real gap.
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, front-loaded sentence with no wasted words. Nothing to trim.
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?
The tool is simple and the schema is complete, so the core mechanics are covered. But with no annotations, no output schema, and a near-identical sibling, the description omits the differentiation an agent most needs before invoking it.
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 schema fully documents query, city, and prefecture, including that the query must be in Japanese. The description's 'by address' only maps to the query param and adds no meaning beyond the schema, so the 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 (search) and resource (postal codes) with the input dimension (by address). However, it does not distinguish itself from the sibling lookup_postal_code, leaving the agent to guess which one to pick.
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?
No guidance on when to prefer this over lookup_postal_code, no stated prerequisites, and no exclusions. The only usage signal is the implicit 'search by address' framing, which is not enough to route between two similar tools.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.