GISFinder API

The GISFinder directory as JSON: which government covers a place, which office handles each job, official links with their last check date, plain-language guides, and screening facts for a point. Free to use, no key needed to start.

API reference Changelog

What it gives you

Every link comes from the directory. Each has official, publisher, verified_status and verified_at. GISFinder checks links on a schedule.
The right office for each job. For a point or a place, the body that assesses, collects tax, records deeds, zones, issues permits and runs the GIS, including towns, townships and districts where the county does not.
Census identifiers. Places use prefixed GEOIDs such as county:27053 and place:2743000.
The same answer for everyone. Results and their order never depend on who asks or which tier a key is on. No office pays to appear or to rank.
The office has the final say. GISFinder is a guide, not an authority. Screening facts are never an official determination.

Quickstart

Base URL https://api.gisfinder.com/v1. Every response is JSON with data, sources, as_of, request_id and notices.

Who handles what at a point (longitude and latitude in WGS84):

curl 'https://api.gisfinder.com/v1/jurisdictions/resolve?lat=44.9778&lon=-93.2650'

The same for an address, or for a place name and state:

curl 'https://api.gisfinder.com/v1/jurisdictions/resolve?address=350+S+5th+St,+Minneapolis,+MN'
curl 'https://api.gisfinder.com/v1/jurisdictions/resolve?place=Two+Harbors&state=MN'

Official resources for a topic, best first:

curl 'https://api.gisfinder.com/v1/resources?jurisdiction_id=county:27053&topic=parcel_map'

A place's full directory, the topic list, a guide with a state's rules, point screening and a name search:

curl 'https://api.gisfinder.com/v1/places/county:27053'
curl 'https://api.gisfinder.com/v1/topics'
curl 'https://api.gisfinder.com/v1/guides/assessor?state=IN'
curl 'https://api.gisfinder.com/v1/screening?lat=45.1&lon=-93.4'
curl 'https://api.gisfinder.com/v1/search?q=web+soil+survey'

The machine-readable description is openapi.json (OpenAPI 3.1), also at https://api.gisfinder.com/v1/openapi.json.

Keys

You can use the API without a key. A key raises your limits; it never changes results. Send it from your server:

curl -H 'Authorization: Bearer YOUR_KEY' 'https://api.gisfinder.com/v1/topics'

Keep keys off web pages. Browsers can call the API without a key from any site; the browser preflight does not allow the Authorization header.

Self-service keys are not open yet. Until then, the limits without a key apply to everyone.

Limits

Caller	Per minute	Per day
No key, per network address (an IPv6 /64 counts as one)	30	1,000
Standard key	120	20,000
Partner key	600	200,000

Every response carries the IETF RateLimit-Policy and RateLimit headers, for example "minute";r=29;t=41: 29 requests left, reset in 41 seconds. Over a limit, the API answers 429 with Retry-After in seconds. Address lookups and screening also share a limit on new outside lookups.

Paging and caching

Long lists (/resources, /places/{jurisdiction_id}) take limit (1 to 100, default 50) and return next_cursor. Pass it back unchanged as cursor with the same other parameters; the Link header with rel="next" holds the same URL. next_cursor is null on the last page.
Responses carry a weak ETag. Send it back in If-None-Match to get 304 Not Modified without a body.
Cache-Control gives how long a response may be reused: a day for topics and guides, an hour for screening, 15 minutes for the rest. Errors are never cached.
Send X-Request-Id (8 to 64 letters, digits, dot, underscore or hyphen) to tag a request; it comes back as request_id.

Errors

Errors are RFC 9457 application/problem+json with type, title, status, detail and request_id. The type is stable; match on it, not on the text.

Type	Status	Meaning
`https://www.gisfinder.com/problems/bad-parameter`	400	A query parameter is missing, has the wrong form, or is out of range.
`https://www.gisfinder.com/problems/bad-point`	400	lat and lon are missing, or are not WGS84 decimal degrees.
`https://www.gisfinder.com/problems/bad-cursor`	400	The cursor was not issued by this endpoint for the same other parameters.
`https://www.gisfinder.com/problems/unknown-topic`	400, 404	The topic is not in the vocabulary at /v1/topics.
`https://www.gisfinder.com/problems/unknown-state`	400	The state code is not a state, DC or territory GISFinder covers.
`https://www.gisfinder.com/problems/invalid-key`	401	The Authorization header is malformed, or the key is unknown or revoked.
`https://www.gisfinder.com/problems/unknown-jurisdiction`	404	No GISFinder place has this jurisdiction_id.
`https://www.gisfinder.com/problems/outside-coverage`	404	The point is not inside a state or territory GISFinder covers.
`https://www.gisfinder.com/problems/address-not-found`	404	No address matched.
`https://www.gisfinder.com/problems/place-not-found`	404	No county, city, town or township with that name in that state.
`https://www.gisfinder.com/problems/not-found`	404	There is no endpoint at this path.
`https://www.gisfinder.com/problems/method-not-allowed`	405	Only GET, HEAD and OPTIONS are answered.
`https://www.gisfinder.com/problems/ambiguous`	409	Several candidates match. The problem lists them in choices; ask again with one of them.
`https://www.gisfinder.com/problems/rate-limited`	429	A minute or day limit is used up. Wait the number of seconds in Retry-After.
`https://www.gisfinder.com/problems/lookup-limit`	429	The limit for new outside lookups (addresses and screening) is used up. Wait the number of seconds in Retry-After.
`https://www.gisfinder.com/problems/internal-error`	500	GISFinder could not finish the request.
`https://www.gisfinder.com/problems/busy`	503	The same lookup is already running, or GISFinder is busy. Retry after a few seconds.
`https://www.gisfinder.com/problems/upstream-unavailable`	503	An outside service GISFinder needs, such as the address geocoder, did not answer.

Using the data

Say that the data comes from GISFinder and link to www.gisfinder.com where you show it.
Show links as they come, with their verification date where you show a status. Links can break; the office named has the final say.
Keep screening labeled as screening, with its caveat.
Directory records whose source GISFinder has not yet documented are left out of API answers, and a notice says how many.
Never send names of people to look up. The API does not search for people.

Versions and deprecation

This is version 1, under /v1. GISFinder adds fields, topics and endpoints without notice, so ignore what you do not recognize. Nothing is removed or changed in meaning without at least 12 months' notice: the change is announced on the changelog, and the affected responses carry Deprecation and Sunset headers for the whole period. A breaking change gets a new version path.

Terms

The API Terms are being written. Until they are published, please follow the points under Using the data.

MCP server

AI assistants can use the directory through the GISFinder MCP server at https://api.gisfinder.com/mcp (Model Context Protocol over Streamable HTTP). It needs no sign-in and never calls a language model itself: every answer comes from the same directory as this API.

Claude: add a custom connector with the URL above, then turn it on in a conversation. In Claude Code: claude mcp add --transport http gisfinder https://api.gisfinder.com/mcp
ChatGPT: add a connector with the URL above and no authentication (developer mode).
Other clients: any MCP client that supports remote Streamable HTTP servers. Its MCP Registry name is com.gisfinder/directory.

Tool	What it answers
`resolve_jurisdiction`	Which state, county, town and city cover an address, point or place, and which office assesses, collects tax, records deeds, zones, issues permits and runs the GIS
`find_official_resource`	The best official page for a topic at a place, with alternatives
`get_place_directory`	Everything listed for one place, grouped by topic
`search_directory`	Places and resources by name
`get_guide`	A plain-language guide and the state's rules
`screen_location`	Flood, wetland, soil, elevation and radon screening at a point, with the office that decides
`get_property_facts`	Parcel facts from PublicGIS where it covers and has cleared the place; never owner names

Each network address can make 30 tool calls a minute and 1,000 a day. Every link carries verified_status and verified_at, and the office named has the final say.

For AI agents

A short description for language models is at /llms.txt.