# Web retrieval tool

**Source:** https://promtable.com/glossary/web-retrieval-tool

> A web retrieval tool is the agent-callable API that fetches live web content for LLMs — Tavily, Exa, Serper, Brave Search API, Perplexity API are 2026 leaders, used as the 'web search' function in tool-use loops.

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A web retrieval tool is the agent-callable API that fetches live web content for LLMs — Tavily, Exa, Serper, Brave Search API, Perplexity API are 2026 leaders, used as the 'web search' function in tool-use loops.

LLMs without web retrieval are stuck at their [[knowledge-cutoff]]. Web retrieval tools fix this: the agent emits a tool call `search(query)`, the tool returns either raw SERPs (Serper, Brave) or pre-summarized answers + citations (Tavily, Perplexity). Trade-offs: raw SERPs give the agent control over what to read but cost more reasoning tokens; pre-summarized answers are cheaper but lossy. Production patterns: voice / phone agents need sub-second latency (Tavily, Perplexity), research agents need depth + citations (Exa, Perplexity), high-volume bulk extraction needs cheapest raw SERPs (Serper). Most agents in 2026 wrap multiple — cheap SERP first, expensive LLM-summarized only when SERP fails.

## When to use

- Any agent needing post-cutoff or live-web information.

## Common mistakes

- Hitting web retrieval on every turn — cache results, only refresh when query is novel.
- Trusting summarized answers without checking citations — LLM-summarized tools can hallucinate.

## Related terms

- [ai-search-engine](https://promtable.com/glossary/ai-search-engine)
- [real-time-knowledge](https://promtable.com/glossary/real-time-knowledge)
- [tool-use](https://promtable.com/glossary/tool-use)

*Last updated: 2026-06-01*
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Original page: https://promtable.com/glossary/web-retrieval-tool
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