United States Postal Service MCP server

• Registry namecom.zip-codes/apiverified in the MCP registry

The registry name sits under zip-codes.com. The registry only lets a publisher use that namespace after proving control of the domain through DNS or HTTP.

• Stateanswerschecked 2026-10-20
• Tools11
• Server calls itselfzip-codes
• Server version1.0.0
• Protocol version2025-06-18

On 2026-10-20 the server answered initialize and tools/list without a sign-in. First answer in 259 ms.

• Whether its tools do the product's job has not been judged yet.

Said by rules from the measurements above. The likely first call is a model's pick from the tool list; read its description before relying on it.

• INITE MCP score85 of 100answers 100 · definitions 100 · context 87 · use 0 · connects 100
• Answered100% of days13 of 13 daily checks
• Median first answer182 ms
• Space in an agent's context≈ 4,876 tokensthe definitions of all its tools (11), which an agent carries on every turn
• Tool definitionsA · 100 of 100
• Typed results0 of 11 toolsdeclared outputSchema: results come typed, read once

• Every tool passes all six checks.

A program checks the server once a day: initialize and tools/list, no model. Tokens are the definitions' length at about four characters a token. The grade averages six checks of every tool's name, description, schema and annotations; it says how well the tools are described, not whether they work. The score weighs what was measured and nothing else: answering (25%), doing the product's job (25%), definitions (20%), context (10%), use (10%) and how readily a client connects (10%). A part that was not measured is left out, and a hidden instruction caps the score at 40. The state of vendors' MCP servers: method and numbers →

• suggest_places

  Search for a place by partial name, misspelled name, or partial code — the resolver that turns what a person typed into something the other tools can look up. Fuzzy matching is built in: "beverley hills" finds Beverly Hills, "san…

• zip_lookup

  The full record for a postal code — the main location-intelligence tool. Takes a US ZIP Code, a US ZIP+4, a Canadian FSA, a Canadian postal code, or a latitude,longitude pair, and returns the city, state or province, county, whether it…

• zip_facts

  Statistics about US ZIP Codes and Canadian postal codes: how many exist, how they break down by type, delivery point and carrier route totals, per-state tables, and ranked lists such as the ZIP Codes with the most carrier routes. Every…

• quick_zip

  The fast, small answer for a postal code. Takes a US ZIP Code, a US ZIP+4, a Canadian FSA, a Canadian postal code, or a latitude,longitude pair, and returns the code's city, state or province, county, and whether it spans more than one…

• city_name_rules

  How USPS names a ZIP Code, and which of those names may be used on mail. Each ZIP Code has exactly one preferred city name plus alternates, and some alternates are NOT valid for addressing — for 08088 NJ, SHAMONG is valid while SHAMONG…

• radius_search

  Find every US ZIP Code and Canadian postal area within a radius of a centre point, with the distance to each. The centre takes a US ZIP Code, a US ZIP+4, a Canadian FSA, a Canadian postal code, or a latitude,longitude pair; a ZIP+4…

• about_data

  Where this server's data comes from: for each dataset the authority behind it, the edition served where the source publishes editions (TIGER/Line, ACS, ZCTA), how often a new release is taken, and a ready-made citation string. Costs…

• distance

  Distance between two places, in miles and kilometres, plus the compass bearing from the first to the second. Each end takes a US ZIP Code, a US ZIP+4, a Canadian FSA, a Canadian postal code, or a latitude,longitude pair, and the two ends…

• validate_address

  Validate and standardise a US street address and return its ZIP+4. US ONLY — unlike the postal-code tools, this does not cover Canada. Send the address on one line in mailing order: number and street, then any unit (APT 4, STE 900, #9)…

• county_reference

  US counties and county equivalents — all 3,235 of them — with their Census and USPS names, which disagree for over a hundred, plus ANSI code, legal type, land and water area, and USPS delivery footprint. Filter by state to get every…

• metro_area_reference

  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…