An LLM knows everything up to its training cutoff and nothing after. Ask it about yesterday's stock price, hand it a PDF, or expect it to tell you which of your 10,000 support tickets are duplicates — and you'll hit a wall. Tools are how you close that gap.

This is article #6 in the series on building AI pipelines with yait_aichain. Three categories today: search for live data, Markdown conversion for universal document ingestion, and embeddings for tasks well beyond basic RAG.

The Design Philosophy: Thin Core, Pluggable Everything

Before any code, one architectural decision is worth understanding. yait_aichain deliberately keeps its core dependency surface small. Only one tool ships inside the package as a hard dependency: Markdown conversion. Everything else — search providers, embeddings, vector stores, rerankers — is either an optional extra you install separately or a pluggable MCP (Model Context Protocol) server running as a separate process.

Why? Specialized tools change fast. Search APIs come and go. OpenAI has shipped three generations of embedding models since 2022, and the pace hasn't slowed. Tying all of that into the core library would create a fragile dependency tree that breaks every time a provider ships a breaking change. So the universal stuff lives inside. The specialized things plug in from outside.

Search: Giving the Model Live Data

A model trained on data through April 2024 can't tell you what happened yesterday. Search tools fix that.

yait_aichain includes a Perplexity search integration as an optional extra. Install it first, then import:

pip install yait-aichain[perplexity]

from yait_aichain.tools import searchPerplexity

search = searchPerplexity()
result = search.run("latest LLM benchmarks 2025")
print(result)

One function call, one string back — grounded, citation-backed, pulled from live web results.

But Perplexity isn't the only option. You might prefer Brave Search for its independence from big-tech indices, or SerpAPI for its structured Google results. These providers connect through MCP servers — external processes that yait_aichain discovers and calls at runtime:

"""
Start the MCP server first:
    python your_newsapi_server.py

MCP server: newsapi on http://127.0.0.1:8009/mcp

Tools available:
    search_news        — search articles (requires: q, sources, or domains)
    get_top_headlines  — breaking news
    get_sources        — list all available news sources
"""

from yait_aichain.tools import Tool
# The Skill/Chain connects to MCP tools via the protocol at runtime.
# No MCP-specific dependencies live inside yait_aichain itself.

The MCP pattern is intentional. A NewsAPI server has its own API key, its own rate limits, its own Python dependencies. Keeping that in a separate process means your core pipeline stays clean. Swap Brave for SerpAPI by pointing at a different MCP server — no code changes in your Chain.

MarkItDownTool: The 80% Solution for Data Prep

Here's a scenario every developer hits: you need an LLM to process a PDF report, a DOCX contract, a PowerPoint deck, and a URL. Each format needs a different parser. Each parser has its own quirks, its own edge cases, its own dependencies.

Or you use one line:

from yait_aichain.tools import convertToMD

tool = convertToMD()

# Convert a URL
web_content = tool.run("https://example.com")
print(web_content[:500])

# Convert a local PDF
pdf_content = tool.run("quarterly_report.pdf")

# Convert a DOCX file
doc_content = tool.run("contract_v3.docx")

Under the hood, convertToMD wraps Microsoft's open-source markitdown library, bundled as a hard dependency of yait_aichain — no separate install required. It handles PDF, DOCX, PPTX, XLSX, HTML, and URLs out of the box. The output is always Markdown, which happens to be the format LLMs consume best.

No configuration objects. No format detection logic. No parsing pipelines. One call turns nearly any document into clean Markdown ready for a Skill or Chain. That's why it's the only tool that lives inside yait_aichain as a hard dependency — document-to-Markdown conversion is universal enough to earn its place in the core.

Embeddings: Beyond Basic RAG

When developers hear "embeddings," they usually think retrieval-augmented generation — chunk documents, embed them, store them in a vector database, retrieve at query time. That's one use case. Not the only one.

from yait_aichain.tools import Embedding

emb = Embedding(model="text-embedding-3-small")
vectors = emb.embed([
    "How do I reset my password?",
    "I can't log into my account",
    "What are your pricing plans?",
    "Password reset not working",
])

Each call returns a list of float vectors. What you do with those vectors determines the use case.

Semantic search. Skip keyword matching entirely. A query for "authentication issues" will surface tickets about password resets, SSO failures, and 2FA problems — because the meaning matches, not the words.

Deduplication. Compare cosine similarity between support tickets. Tickets 0, 1, and 3 above will cluster tightly — they're semantically identical despite different wording. Set a similarity threshold of 0.92 and you can automatically flag duplicates across thousands of entries without a human reading a single one.

Clustering. Feed the vectors into k-means or HDBSCAN. Group product reviews by theme without writing a single regex. Find natural topic boundaries in a corpus of research papers.

The VectorDB class gives you an in-process vector store for quick prototyping:

from yait_aichain.tools import VectorDB, vectorQuery

db = VectorDB()
db.add(
    documents=["Password reset guide", "Pricing FAQ", "SSO troubleshooting"],
    ids=["d1", "d2", "d3"],
)

results = vectorQuery(db, query="I can't log in", top_k=2)
for r in results:
    print(r)

Note: vectorQuery is a standalone function rather than a method on VectorDB because it operates across multiple database instances in pipeline contexts — the separation is intentional.

When result quality matters and your document set is large, add a reranking step:

from yait_aichain.tools import Reranker

reranker = Reranker()
ranked = reranker.rerank(
    query="latest AI benchmarks",
    documents=["doc A about benchmarks", "doc B about pricing", "doc C about model eval"],
)
print(ranked)

The reranker takes coarse results from vector search and reorders them with a cross-encoder — more expensive per comparison, but on published benchmarks like BEIR, cross-encoder reranking consistently improves precision at top-k positions over vector search alone. Think of results as your candidate pool and ranked as the final ordered list you pass to the model.

Custom Tools: Build Your Own

Every tool in yait_aichain follows the same pattern: subclass Tool, define name and description, implement run(self, input: str). The single-string signature is what lets the framework invoke your tool through the standard LLM tool-calling protocol — the model sends a string (or a JSON blob you parse yourself), your tool returns a string. Here's a live currency exchange tool:

import json
import urllib3
from yait_aichain.tools import Tool
from yait_aichain import Model, Skill

class FXRateTool(Tool):
    """Fetch live FX rate from frankfurter.app."""
    name = "fx_rate"
    description = (
        "Return the current exchange rate between two currencies. "
        "Input must be a JSON string with keys 'base' and 'target', "
        "e.g. '{\"base\": \"USD\", \"target\": \"EUR\"}'."
    )

    def run(self, input: str) -> str:
        # Production code should validate input and handle network errors.
        params = json.loads(input)
        base = params.get("base", "USD")
        target = params.get("target", "EUR")
        http = urllib3.PoolManager()
        resp = http.request(
            "GET",
            f"https://api.frankfurter.app/latest?from={base}&to={target}",
        )
        data = json.loads(resp.data.decode())
        rate = data["rates"][target]
        return f"1 {base} = {rate} {target}"

# Use it standalone
tool = FXRateTool()
print(tool.run('{"base": "USD", "target": "EUR"}'))  # 1 USD = 0.8842 EUR

# Or plug it into a Skill
model = Model("claude-3-5-sonnet-20241022")
skill = Skill(
    model=model,
    input={
        "messages": [
            {
                "role": "user",
                # yait_aichain uses "content" as the universal message field
                # across all supported providers.
                "content": "What is the USD to EUR rate? Use the fx_rate tool.",
            }
        ]
    },
    tools=[FXRateTool()],
)

The tools=[] parameter on Skill accepts any list of Tool instances. The model sees the tool names and descriptions, decides when to call them, and incorporates the results into its response. You write the logic once. The framework handles the tool-calling protocol across all eight supported providers — OpenAI, Anthropic, Google Gemini, xAI Grok, Mistral, Groq, Ollama, and any OpenAI-compatible endpoint.

What Lives Where

The boundary is deliberate. Markdown conversion is universal — every pipeline needs to ingest documents. Search providers, embedding models, and vector stores are opinionated choices that vary by project. Keep them outside and your base pip install yait-aichain stays light. Add only what you actually use.

Tools extend what a language model can do: read today's news, parse your company's PDFs, find semantic patterns across thousands of documents. The API surface stays small. The capabilities grow with your project.