google-gemini-file-search

Google Gemini File Search Setup

Overview

Google Gemini File Search is a fully managed RAG system. Upload documents (100+ formats: PDF, Word, Excel, code) and query with natural language—automatic chunking, embeddings, semantic search, and citations.

What This Skill Provides:

• Complete @google/genai File Search API setup
• 8 documented errors with prevention strategies
• Chunking best practices for optimal retrieval
• Cost optimization ($0.15/1M tokens indexing, 3x storage multiplier)
• Cloudflare Workers + Next.js integration templates

Prerequisites

1. Google AI API Key

Create an API key at https://aistudio.google.com/apikey

Free Tier Limits:

• 1 GB storage (total across all file search stores)
• 1,500 requests per day
• 1 million tokens per minute

Paid Tier Pricing:

• Indexing: $0.15 per 1M input tokens (one-time)
• Storage: Free (Tier 1: 10 GB, Tier 2: 100 GB, Tier 3: 1 TB)
• Query-time embeddings: Free (retrieved context counts as input tokens)

2. Node.js Environment

Minimum Version: Node.js 18+ (v20+ recommended)

node --version  # Should be >=18.0.0

3. Install @google/genai SDK

npm install @google/genai
# or
pnpm add @google/genai
# or
yarn add @google/genai

Current Stable Version: 1.30.0+ (verify with npm view @google/genai version)

⚠️ Important: File Search API requires @google/genai v1.29.0 or later. Earlier versions do not support File Search. The API was added in v1.29.0 (November 5, 2025).

4. TypeScript Configuration (Optional but Recommended)

{
  "compilerOptions": {
    "target": "ES2020",
    "module": "ESNext",
    "moduleResolution": "node",
    "esModuleInterop": true,
    "strict": true,
    "skipLibCheck": true
  }
}

Common Errors Prevented

This skill prevents 8 common errors encountered when implementing File Search:

Error 1: Document Immutability

Symptom:

Error: Documents cannot be modified after indexing

Cause: Documents are immutable once indexed. There is no PATCH or UPDATE operation.

Prevention: Use the delete+re-upload pattern for updates:

// ❌ WRONG: Trying to update document (no such API)
await ai.fileSearchStores.documents.update({
  name: documentName,
  customMetadata: { version: '2.0' }
})

// ✅ CORRECT: Delete then re-upload
const docs = await ai.fileSearchStores.documents.list({
  parent: fileStore.name
})

const oldDoc = docs.documents.find(d => d.displayName === 'manual.pdf')
if (oldDoc) {
  await ai.fileSearchStores.documents.delete({
    name: oldDoc.name,
    force: true
  })
}

await ai.fileSearchStores.uploadToFileSearchStore({
  name: fileStore.name,
  file: fs.createReadStream('manual-v2.pdf'),
  config: { displayName: 'manual.pdf' }
})

Source: https://ai.google.dev/api/file-search/documents

Error 2: Storage Quota Exceeded

Symptom:

Error: Quota exceeded. Expected 1GB limit, but 3.2GB used.

Cause: Storage calculation includes input files + embeddings + metadata. Total storage ≈ 3x input size.

Prevention: Calculate storage before upload:

// ❌ WRONG: Assuming storage = file size
const fileSize = fs.statSync('data.pdf').size // 500 MB
// Expect 500 MB usage → WRONG

// ✅ CORRECT: Account for 3x multiplier
const fileSize = fs.statSync('data.pdf').size // 500 MB
const estimatedStorage = fileSize * 3 // 1.5 GB (embeddings + metadata)
console.log(`Estimated storage: ${estimatedStorage / 1e9} GB`)

// Check if within quota before upload
if (estimatedStorage > 1e9) {
  console.warn('⚠️ File may exceed free tier 1 GB limit')
}

Source: https://blog.google/technology/developers/file-search-gemini-api/

Error 3: Incorrect Chunking Configuration

Symptom: Poor retrieval quality, irrelevant results, or context cutoff mid-sentence.

Cause: Default chunking may not be optimal for your content type.

Prevention: Use recommended chunking strategy:

// ❌ WRONG: Using defaults without testing
await ai.fileSearchStores.uploadToFileSearchStore({
  name: fileStore.name,
  file: fs.createReadStream('docs.pdf')
  // Default chunking may be too large or too small
})

// ✅ CORRECT: Configure chunking for precision
await ai.fileSearchStores.uploadToFileSearchStore({
  name: fileStore.name,
  file: fs.createReadStream('docs.pdf'),
  config: {
    chunkingConfig: {
      whiteSpaceConfig: {
        maxTokensPerChunk: 500,  // Smaller chunks = more precise retrieval
        maxOverlapTokens: 50     // 10% overlap prevents context loss
      }
    }
  }
})

Chunking Guidelines:

• Technical docs/code: 500 tokens/chunk, 50 overlap
• Prose/articles: 800 tokens/chunk, 80 overlap
• Legal/contracts: 300 tokens/chunk, 30 overlap (high precision)

Source: https://www.philschmid.de/gemini-file-search-javascript

Error 4: Metadata Limits Exceeded

Symptom:

Error: Maximum 20 custom metadata key-value pairs allowed

Cause: Each document can have at most 20 metadata fields.

Prevention: Design compact metadata schema:

// ❌ WRONG: Too many metadata fields
await ai.fileSearchStores.uploadToFileSearchStore({
  name: fileStore.name,
  file: fs.createReadStream('doc.pdf'),
  config: {
    customMetadata: {
      doc_type: 'manual',
      version: '1.0',
      author: 'John Doe',
      department: 'Engineering',
      created_date: '2025-01-01',
      // ... 18 more fields → Error!
    }
  }
})

// ✅ CORRECT: Use hierarchical keys or JSON strings
await ai.fileSearchStores.uploadToFileSearchStore({
  name: fileStore.name,
  file: fs.createReadStream('doc.pdf'),
  config: {
    customMetadata: {
      doc_type: 'manual',
      version: '1.0',
      author_dept: 'John Doe|Engineering',  // Combine related fields
      dates: JSON.stringify({                // Or use JSON for complex data
        created: '2025-01-01',
        updated: '2025-01-15'
      })
    }
  }
})

Source: https://ai.google.dev/api/file-search/documents

Error 5: Indexing Cost Surprises

Symptom: Unexpected bill for $375 after uploading 10 GB of documents.

Cause: Indexing costs are one-time but calculated per input token ($0.15/1M tokens).

Prevention: Estimate costs before indexing:

// ❌ WRONG: No cost estimation
await uploadAllDocuments(fileStore.name, './data') // 10 GB uploaded → $375 surprise

// ✅ CORRECT: Calculate costs upfront
const totalSize = getTotalDirectorySize('./data') // 10 GB
const estimatedTokens = (totalSize / 4) // Rough estimate: 1 token ≈ 4 bytes
const indexingCost = (estimatedTokens / 1e6) * 0.15

console.log(`Estimated indexing cost: $${indexingCost.toFixed(2)}`)
console.log(`Estimated storage: ${(totalSize * 3) / 1e9} GB`)

// Confirm before proceeding
const proceed = await confirm(`Proceed with indexing? Cost: $${indexingCost.toFixed(2)}`)
if (proceed) {
  await uploadAllDocuments(fileStore.name, './data')
}

Cost Examples:

• 1 GB text ≈ 250M tokens = $37.50 indexing
• 100 MB PDF ≈ 25M tokens = $3.75 indexing
• 10 MB code ≈ 2.5M tokens = $0.38 indexing

Source: https://ai.google.dev/pricing

Error 6: Not Polling Operation Status

Symptom: Query returns no results immediately after upload, or incomplete indexing.

Cause: File uploads are processed asynchronously. Must poll operation until done: true.

Prevention: Always poll operation status:

// ❌ WRONG: Assuming upload is instant
const operation = await ai.fileSearchStores.uploadToFileSearchStore({
  name: fileStore.name,
  file: fs.createReadStream('large.pdf')
})
// Immediately query → No results!

// ✅ CORRECT: Poll until indexing complete
const operation = await ai.fileSearchStores.uploadToFileSearchStore({
  name: fileStore.name,
  file: fs.createReadStream('large.pdf')
})

// Poll every 1 second
while (!operation.done) {
  await new Promise(resolve => setTimeout(resolve, 1000))
  operation = await ai.operations.get({ name: operation.name })
  console.log(`Indexing progress: ${operation.metadata?.progress || 'processing...'}`)
}

if (operation.error) {
  throw new Error(`Indexing failed: ${operation.error.message}`)
}

console.log('✅ Indexing complete:', operation.response.displayName)

Source: https://ai.google.dev/api/file-search/file-search-stores#uploadtofilesearchstore

Error 7: Forgetting Force Delete

Symptom:

Error: Cannot delete store with documents. Set force=true.

Cause: Stores with documents require force: true to delete (prevents accidental deletion).

Prevention: Always use force: true when deleting non-empty stores:

// ❌ WRONG: Trying to delete store with documents
await ai.fileSearchStores.delete({
  name: fileStore.name
})
// Error: Cannot delete store with documents

// ✅ CORRECT: Use force delete
await ai.fileSearchStores.delete({
  name: fileStore.name,
  force: true  // Deletes store AND all documents
})

// Alternative: Delete documents first
const docs = await ai.fileSearchStores.documents.list({ parent: fileStore.name })
for (const doc of docs.documents || []) {
  await ai.fileSearchStores.documents.delete({
    name: doc.name,
    force: true
  })
}
await ai.fileSearchStores.delete({ name: fileStore.name })

Source: https://ai.google.dev/api/file-search/file-search-stores#delete

Error 8: Using Unsupported Models

Symptom:

Error: File Search is only supported for Gemini 2.5 Pro and Flash models

Cause: File Search requires Gemini 2.5 Pro or Gemini 2.5 Flash. Gemini 1.5 models are not supported.

Prevention: Always use 2.5 models:

// ❌ WRONG: Using Gemini 1.5 model
const response = await ai.models.generateContent({
  model: 'gemini-1.5-pro',  // Not supported!
  contents: 'What is the installation procedure?',
  config: {
    tools: [{
      fileSearch: { fileSearchStoreNames: [fileStore.name] }
    }]
  }
})

// ✅ CORRECT: Use Gemini 2.5 models
const response =

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*Content truncated.*