Choosing a retrieval API for RAG and agents

Retrieval APIs for RAG and agents all promise the same thing: fresh web data an LLM can ground its answer in. The real buying decision is narrower than it looks — almost every vendor here is usage-based and cloud-only, so the differences that actually separate them are MCP support, agent-readiness, and how much compliance backing is attached to the API.

What to actually compare

Usage-based pricing, with one exception. Perplexity Sonar API, Exa, Brave Search API, and You.com all start at $5–7 on usage-based billing with no subscription commitment. Serper breaks that pattern with a $50 one-time/prepaid model instead of ongoing usage billing. Tavily is the one vendor here that requires a sales call and publishes no starting price at all, despite offering a free tier to start.

MCP support is close to universal, but not complete. Perplexity Sonar API, Exa, Tavily, and Brave Search API all have a public MCP server repo you can inspect directly. You.com also has an MCP server, though without a listed public repo. Serper is the one vendor in this category without an MCP server.

Agent-readiness varies more than pricing does. Perplexity Sonar API leads at 87, followed by Exa (80), Tavily (79), Brave Search API (76), and You.com (74) — a tight cluster. Serper trails at 59, consistent with it being the only vendor without both a free tier that doesn’t require a sales call to convert and an MCP server (Tavily has a free tier but gates paid conversion behind a sales call).

Compliance backing, if you’re grounding regulated workflows. Perplexity Sonar API carries the most: SOC 2 Type II, a 2025 HIPAA gap assessment, and CAIQ-Lite. Brave Search API and You.com both carry SOC 2 (Type II for Brave). Exa, Tavily, and Serper list no compliance certifications in Crail’s data.

Where to start

Compare current pricing, MCP support, and agent-readiness scores for every vendor on the AI Search & Retrieval APIs category page, or see a direct side-by-side in Perplexity Sonar API vs Exa.