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Zip-Codes.com Location Intelligence: Spatial Analysis, Districts & 14+ Years of Demographics

by com.zip-codes
OverviewDiscussionsAdmin

Metro area reference

metro_area_reference
Read-onlyIdempotent

US metropolitan and micropolitan statistical areas (CBSAs) — all 935. Of those only 393 are metropolitan; the rest are micropolitan and are NOT metro areas, so do not treat a CBSA count as a metro count. Each carries its divisions, parent combined area, land area and delivery footprint, plus the CMS Medicare labor market area, which is a DIFFERENT geography that shares the same code space. Filter by state to get every area in that state: without a filter only the first 25 are returned, alphabetically, so an unfiltered call answers with Aberdeen. Costs nothing and needs no key.

Tool call template

This tool declares no required parameters. Add optional parameters from the input schema as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {},
    "name": "metro_area_reference"
  }
}

Input Schema

NameRequiredDescriptionDefault
limitNoCap the number of areas returned. Defaults to 25 when no state is given, or to all areas in the state when one is.
stateNoTwo-letter US state or territory code. Returns every area that includes that state — an area can span several, so it is matched against the area's whole state list. Omit to browse all states.

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observed

TDQS

A4.7/5.0
Behavior5/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already cover read-only/idempotent/no-auth profile, but the description adds meaningful context beyond them: the 25-row default, alphabetical ordering (first result is Aberdeen), the dual geography code space, and that the call is free and keyless. These are exactly the details that prevent misfires.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Four dense sentences, front-loaded with the resource scope, then the metro/micropolitan caveat, then the filter/default behavior. No filler; each clause adds operational value.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

No output schema exists, yet the description enumerates the returned fields (divisions, parent combined area, land area, delivery footprint, CMS labor market area). Combined with the default/pagination warnings, an agent has everything needed to call it correctly.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100% and already documents the limit default and state enum. The description reinforces the state match semantics (an area spans multiple states, so it matches the whole state list), adding a nuance beyond the schema's wording.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States the exact resource (US CBSAs, all 935) and immediately disambiguates metropolitan vs micropolitan, which is the main confusion risk. An agent knows precisely what dataset this returns without opening the schema.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives clear when-to-use guidance: filter by state to retrieve a full state's areas, and warns that an unfiltered call returns only the first 25 alphabetical entries. It does not name sibling tools (county_reference, zip_facts) as alternatives, so it falls just short of a 5.

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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