Best Transcription API for AI Agents (2026 Comparison)

Building an AI agent that needs to transcribe audio? This guide compares the top three transcription APIs with real benchmarks, pricing, and working code.

Quick Comparison

Service	Speed	Cost/Hour	Best For
Groq Whisper	Fastest (10x realtime)	$0.06	Speed-critical apps
Deepgram	Fast (3x realtime)	$0.26	Balance of speed/accuracy
AssemblyAI	Medium (1x realtime)	$0.36	Highest accuracy

Groq Whisper — Fastest Option

Groq runs Whisper on custom LPU hardware, achieving 10x realtime speed at the lowest cost.

Pros:

• Fastest transcription available
• Lowest price per minute
• OpenAI Whisper compatibility

Cons:

• No speaker diarization
• No real-time streaming

Code Example (TypeScript)

import Groq from 'groq-sdk';

const groq = new Groq({ apiKey: process.env.GROQ_API_KEY });

async function transcribe(audioUrl: string): Promise<string> {
  const response = await groq.audio.transcriptions.create({
    file: await fetch(audioUrl).then(r => r.blob()),
    model: "whisper-large-v3",
  });
  return response.text;
}

Deepgram — Best Balance

Deepgram offers the best combination of speed, accuracy, and features for most use cases.

Pros:

• Real-time streaming support
• Speaker diarization included
• Multiple model options

Cons:

• Higher cost than Groq
• Requires API key management

Code Example (TypeScript)

import { createClient } from '@deepgram/sdk';

const deepgram = createClient(process.env.DEEPGRAM_API_KEY);

async function transcribe(audioUrl: string): Promise<string> {
  const { result } = await deepgram.listen.prerecorded.transcribeUrl(
    { url: audioUrl },
    { model: "nova-2", smart_format: true }
  );
  return result.results.channels[0].alternatives[0].transcript;
}

AssemblyAI — Highest Accuracy

AssemblyAI leads in accuracy, especially for complex audio with multiple speakers or technical content.

Pros:

• Best accuracy for difficult audio
• Built-in summarization
• LeMUR for Q&A on transcripts

Cons:

• Slower than alternatives
• Higher price point

Code Example (TypeScript)

import { AssemblyAI } from 'assemblyai';

const client = new AssemblyAI({ apiKey: process.env.ASSEMBLYAI_API_KEY });

async function transcribe(audioUrl: string): Promise<string> {
  const transcript = await client.transcripts.transcribe({ audio_url: audioUrl });
  return transcript.text;
}

How to Get API Keys Automatically

AI agents can sign up for these services autonomously using Portal:

// Using Portal MCP server
const result = await portal.signup({ service: "deepgram" });
console.log(result.credentials.api_key);

No human intervention needed. Portal handles the signup flow and returns credentials in under 30 seconds.

Recommendation

• Speed-critical: Use Groq Whisper
• General purpose: Use Deepgram Nova-2
• Accuracy-critical: Use AssemblyAI

All three services are indexed in Portal with verified code snippets and autonomous signup support.