Reference data for AI

Ground provides structured, accurate data that AI assistants access directly via MCP. Classification systems, hierarchical encodings, and real-world catalogs — the kind of precise information that's too specialized and hit-or-miss for training data and too structured to work well in web searches.

Get Started API Documentation

What's available

Ground currently covers three types of reference data, with more in development.

360+
Classification systems
7,000+
Hierarchical codes
85+
Domain categories
Live

Classification Systems

Discrete value sets with defined relationships. Wire gauges, IP ratings, shoe sizes, thread standards, battery types, and hundreds more. Query values, convert between related systems.

Live

Measurement Conversions

Continuous scales with formula-based conversion. Temperature, pressure, length, mass, volume. Convert any value between related units with verified formulas.

Live

Encoding Systems

Hierarchical code structures with parent-child relationships. HS codes for international trade, with ICD-10, NAICS, and other standard taxonomies in development.

Coming soon

Real-World Catalogs

Registries of physical things. Ships by hull number, aircraft by registration, products by UPC. Including real-time observations where available — tide levels, positions, status.

Connect your AI assistant

Ground uses the Model Context Protocol (MCP) to integrate directly with AI assistants. Your assistant queries Ground for facts instead of guessing. View on MCP Registry

Server URL

https://mcp.ground.fyi/mcp

Setup steps

  1. Open claude.ai and go to Settings
  2. Select Connectors in the sidebar
  3. Click Add custom connector at the bottom
  4. Paste the server URL above and click Add
  5. Click Connect and complete the signup flow to create your Ground account
  6. Click Allow to grant Claude access

Once connected, enable Ground via the + button in your chat and select it from Connectors.

Available on Claude Pro, Max, Team, and Enterprise plans.

Server URL

https://mcp.ground.fyi/mcp

Setup steps

  1. Open Claude Desktop and go to Settings
  2. Select Connectors in the sidebar
  3. Click Add custom connector
  4. Paste the server URL above and click Add
  5. Click Connect and complete the signup flow to create your Ground account
  6. Click Allow to grant Claude access

Once connected, Ground tools are automatically available in all conversations.

Available on Claude Pro, Max, Team, and Enterprise plans.

Server URL

https://mcp.ground.fyi/mcp

Setup steps

  1. Go to Settings → Apps & Connectors
  2. Under Advanced settings, enable Developer Mode
  3. Click Create to add a new connector
  4. Enter a name (e.g., "Ground") and paste the server URL above
  5. Complete the signup flow to create your Ground account
  6. Authorize access when prompted

To use Ground in a chat, click the + button, select More, and choose your connector.

Available on ChatGPT Pro, Plus, Team, Enterprise, and Edu plans. Requires Developer Mode.

Server URL

https://mcp.ground.fyi/mcp

Connection details

Any MCP-compatible client can connect using:

  • Transport: Streamable HTTP
  • Authentication: OAuth 2.0 with PKCE
  • OAuth metadata: /.well-known/oauth-authorization-server
  • Scopes: catalog:read, catalog:write
Gemini web app does not yet support custom MCP servers. Gemini CLI users can configure the server manually.
Example query
"What's the metric equivalent of 12 AWG wire?"

REST API

For developers building applications, Ground provides a straightforward REST API with OpenAPI documentation.

Query domains

Search and filter across all reference data domains. Full-text search, semantic search, and structured filtering by category, type, and status.

Look up values

Get detailed information about specific codes and values. Metadata, relationships, equivalent values in other systems.

Convert between systems

Convert values between related systems using verified formulas and equivalence mappings. Works for both continuous measurements and discrete classifications.

Navigate hierarchies

Traverse parent-child relationships in encoding systems. Get ancestors, descendants, or siblings of any code.

Coming soon

Ground is expanding to cover more of the structured data that AI needs to be reliable.

Browsable database

A public website for exploring Ground's data directly. Browse domains, search values, understand relationships — similar to how you might browse Wikipedia.

Real-time observations

Live data attached to catalog entries. Current tide levels at NOAA stations, aircraft positions, weather observations. Historical data for trend analysis.

Cross-system mappings

Equivalences and crosswalks between related systems. ICD-9 to ICD-10 mappings, NAICS to SIC codes, and other standard translations.

Expanded catalogs

More registries of real-world entities. FAA aircraft registry, maritime vessel databases, product identifiers, geographic codes.

Pricing

Simple, flat-rate pricing. No per-request fees, no usage tiers.

$3/month
or $30/year
  • Full API access
  • All classification systems
  • All measurement conversions
  • All encoding systems
  • MCP integration
  • 10,000 requests/hour
Start free trial
Early access: Free access available for users who can provide constructive feedback as we prepare for public launch.