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The Gravity Index is a discovery API that AI agents call when a user needs something the agent can’t produce itself: a database, an email API, a pair of running shoes. One publisher key, two verticals: For developer services it’s not a search engine; it’s a reasoning agent that understands what you’re building and recommends the best tool, with the reasoning behind the pick. For products it’s structured retrieval: filters for brand, merchant, price and sale status, ranked by relevance.

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Who can integrate

Any approved Gravity publisher. Your existing publisher API key works on every Index endpoint the moment your account is approved for production traffic; there is no separate Index sign-up or entitlement. Blocked accounts get 403 on every Index call, the same gate that applies to production ads.

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How it works

1

Agent searches

Your AI coding agent calls POST /search with a natural language query like “I need a serverless database with a free tier.”
2

Index reasons

The Gravity Index analyzes the catalog, considers your constraints, and picks the best match — explaining why it’s the right choice.
3

Agent presents the recommendation

The response includes the recommended service, the reasoning, and a tracked link. The agent surfaces it to the user in its own words.
4

User follows the link

The user clicks the tracked link to sign up with the service. Attribution is recorded on that click; billing only happens after a confirmed conversion.

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Set up in 30 seconds

Set up

Pick your surface (MCP server, bash CLI, or direct API) and get running in under a minute.

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Interfaces

MCP Server

npx -y @gravity-ai/index-mcp — native tool for Cursor, Claude Code, Claude Desktop, Windsurf

Bash CLI

gravity-index search "database" — terminal + scripts

REST API

POST index.trygravity.ai/search — custom integrations

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Base URL

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Key concepts

  • search_id — every search gets a unique ID. Pass it back for follow-up questions. The Index remembers context.
  • Click link: a tracked short URL the user clicks to sign up with the recommended service. It mints a grclid for attribution; billing only happens after a confirmed conversion.
  • Conversation context: pass your stable external_session_id and the Index uses that session’s cached summary as private supporting context. See Conversation context.
  • No auction — pure relevance matching with reasoning. Not bidding.