Tools and APIs for Building Powerful AI Agents in 2025

AI agents are everywhere these days, but how are these agents built? What tools and API's are being used? Well lets just quickly overview of what AI Agents are and then go through all the tools that are being used for building these. Think of them as your new digital teammates, quietly working away in the background. They’re researching, digging through data, scraping websites, or even tapping into APIs to get stuff done.

It’s pretty amazing to see how far they’ve come! But if you’re looking to build one of these clever, self-sufficient agents, whether it’s a research assistant, a market analyst bot, or a voice-powered helper, you’ll need the right set of tools.

Here’s a breakdown of key tools that can be used via API's, categorized by function—so you can build agents that aren’t just smart, but efficiently autonomous.

🔍 Web Search APIs: For Real-Time Intelligence

AI agents need access to up-to-date information. These search APIs help the agent to get fresh, real-time info to stay sharp:

• Tavily: Tailored for AI agents, Tavily offers structured search results with clean metadata—no fluff, just facts. Perfect for agents that need to synthesize or cite live data.
• Exa: Designed with AI workflows in mind, Exa goes beyond keyword search. It retrieves relevant documents and pages using semantic search, which pairs well with LLM-driven summarization.
• DuckDuckGo (DDG) API: A privacy-respecting search API that returns links, snippets, and instant answers without tracking. Simple and effective for lightweight lookups.
  

Use Case:
A research agent that needs to pull recent articles, summarize them, and answer user queries accurately.

Note: If you are looking to automate your work using these tools in a no code way, we built Athina Flows for you to automate your linear tasks and Athina Sheets for you to automate your work at scale. Check out Flows and Sheets.

🕸 Web Scraping: Getting the Raw Web

Sometimes search results just don’t give you the full picture, your agent needs to dig a little deeper. That’s when scraping tools step in:

• Spidercrawl: A powerful crawler built for AI. It handles JavaScript-heavy pages and extracts structured data from deep links. Great for large-scale scraping tasks.
• Firecrawl: Built with AI in mind, Firecrawl doesn’t just fetch web pages—it preprocesses and summarizes content, reducing load on the LLM.

Use Case:
A market-monitoring agent that pulls data from competitor websites, product listings, or regulatory bulletins.

📄 Parsing and Structuring Data

Raw text isn’t enough. Agents need to understand and structure information.

• LlamaParse: Developed by the team behind LlamaIndex, this parser takes messy PDFs, HTML, or scraped text and turns it into structured chunks optimized for vector indexing or LLM prompts.
• Unstructured: Unstructured specializes in breaking down complex documents—like PDFs, Word files, or web pages—into clean, usable data. It’s a go-to for agents that need to process diverse file types with ease.

Use Case:
An enterprise agent that reads contracts, invoices, or whitepapers and extracts actionable insights.

📚 Research APIs: Real-Time, Cited, and Smart

When you need high-quality answers with citations:

• Perplexity API: One of the most accurate and LLM-aligned research tools out there. It combines web search, document retrieval, and grounded answers, all with links. Perfect for agents that must explain their reasoning or cite sources.
• Google Scholar API: A reliable choice for academic-grade research, this API pulls peer-reviewed papers, citations, and scholarly content. It’s ideal for agents tackling in-depth, credible investigations.

Use Case:
A legal research assistant or academic agent that needs to verify facts and cite scholarly or public sources.

📊 Finance & Crypto APIs: Real-Time Market Intel

If your agent’s focused on finance or crypto, these APIs bring real-time market smarts:

• YFinance: A go-to API for real-time and historical stock market data, earnings, dividends, and financial statements. Easy to plug into trading bots or dashboards.
• CoinCap: A fast and free API for live cryptocurrency data. Offers prices, volumes, and market caps for thousands of coins.

Use Case:
An investment agent monitoring stocks or crypto trends and making real-time portfolio decisions.

🔉 Text-to-Speech: Giving Your Agent a Voice

Want your agent to talk back? These TTS tools bring realistic, human-like voices to the table:

• Eleven Labs: Industry-leading TTS with ultra-realistic, emotionally expressive voices. You can also clone voices for custom use cases.
• Play HT: A strong competitor with a wide range of accents, emotions, and voice styles. It’s fast and API-friendly.

Use Case:
A voice-powered customer support agent or accessibility tool that reads documents aloud.

🧠 LLM Providers: The Brains Behind the Agent

You need a strong LLM backend to drive reasoning, summarization, and decision-making. These 2 providers helps you get started for free:

• Google AI Studio: Platform by Google to play around with Google's AI Models, complete with memory and retrieval features. It offers free APIs, like Gemini, with up to 60 requests per second (3,600 per minute) to get going.
• Groq: The king of speed, Groq runs LLM inference at blazing fast speeds (100+ tokens/ms) providing both Open Source and Closed Source Models as API's, perfect for latency-sensitive agents.

Final Thoughts

We’re in the golden age of AI agents—but building great ones is all about connecting the right tools. From real-time search to parsing, TTS, and blazing-fast inference, the ecosystem is finally mature enough to create truly autonomous systems.

Whether you’re building your first research bot or a voice-enabled financial assistant, this toolbox will help you go from idea to execution—fast.