Workers Binding Validator

Workers Binding Validator SKILL

Activation Patterns

This SKILL automatically activates when:

• env parameter is used in Workers code
• wrangler.toml file is modified
• TypeScript Env interface is defined or updated
• New binding references are added to code
• Binding configuration patterns are detected

Expertise Provided

Binding Configuration Validation

• Binding Consistency: Ensures code references match wrangler.toml configuration
• TypeScript Interface Validation: Validates Env interface matches actual bindings
• Binding Type Accuracy: Ensures correct binding types (KV, R2, D1, Durable Objects)
• Remote Binding Validation: Checks remote binding configuration for development
• Secret Binding Verification: Validates secret vs environment variable bindings

Specific Checks Performed

❌ Critical Binding Mismatches

// These patterns trigger immediate alerts:
// Code references binding that doesn't exist in wrangler.toml
const user = await env.USER_DATA.get(id);  // USER_DATA not configured

// TypeScript interface doesn't match wrangler.toml
interface Env {
  USERS: KVNamespace;     // Code expects USERS
  // wrangler.toml has USER_DATA (mismatch!)
}

✅ Correct Binding Patterns

// These patterns are validated as correct:
// Matching wrangler.toml and TypeScript interface
interface Env {
  USER_DATA: KVNamespace;  // Matches wrangler.toml binding name
  API_BUCKET: R2Bucket;    // Correct R2 binding type
}

// Proper usage in code
const user = await env.USER_DATA.get(id);
const object = await env.API_BUCKET.get(key);

Integration Points

Complementary to Existing Components

• binding-context-analyzer agent: Handles complex binding analysis, SKILL provides immediate validation
• workers-runtime-validator SKILL: Complements runtime checks with binding validation
• cloudflare-security-checker SKILL: Ensures secret bindings are properly configured

Escalation Triggers

• Complex binding architecture questions → binding-context-analyzer agent
• Migration between binding types → cloudflare-architecture-strategist agent
• Binding performance issues → edge-performance-oracle agent

Validation Rules

P1 - Critical (Will Fail at Runtime)

• Missing Bindings: Code references bindings not in wrangler.toml
• Type Mismatches: Wrong binding types in TypeScript interface
• Name Mismatches: Different names in code vs configuration
• Missing Env Interface: No TypeScript interface for bindings

P2 - High (Configuration Issues)

• Remote Binding Missing: Development bindings without remote = true
• Secret vs Var Confusion: Secrets in [vars] section or vice versa
• Incomplete Interface: Missing bindings in TypeScript interface

P3 - Medium (Best Practices)

• Binding Documentation: Missing JSDoc comments for bindings
• Binding Organization: Poor organization of related bindings

Remediation Examples

Fixing Missing Bindings

// ❌ Critical: Code references binding not in wrangler.toml
export default {
  async fetch(request: Request, env: Env) {
    const user = await env.USER_CACHE.get(userId); // USER_CACHE not configured!
  }
}

// wrangler.toml (missing binding)
[[kv_namespaces]]
binding = "USER_DATA"  # Different name!
id = "user-data"

// ✅ Correct: Matching names
export default {
  async fetch(request: Request, env: Env) {
    const user = await env.USER_DATA.get(userId); // Matches wrangler.toml
  }
}

// wrangler.toml (correct binding)
[[kv_namespaces]]
binding = "USER_DATA"  # Matches code!
id = "user-data"

Fixing TypeScript Interface Mismatches

// ❌ Critical: Interface doesn't match wrangler.toml
interface Env {
  USERS: KVNamespace;      // Code expects USERS
  SESSIONS: KVNamespace;    // Code expects SESSIONS
}

// wrangler.toml has different names
[[kv_namespaces]]
binding = "USER_DATA"      # Different!
id = "user-data"

[[kv_namespaces]]
binding = "SESSION_DATA"    # Different!
id = "session-data"

// ✅ Correct: Matching interface and configuration
interface Env {
  USER_DATA: KVNamespace;   # Matches wrangler.toml
  SESSION_DATA: KVNamespace; # Matches wrangler.toml
}

// wrangler.toml (matching names)
[[kv_namespaces]]
binding = "USER_DATA"       # Matches interface!
id = "user-data"

[[kv_namespaces]]
binding = "SESSION_DATA"     # Matches interface!
id = "session-data"

Fixing Binding Type Mismatches

// ❌ Critical: Wrong binding type
interface Env {
  MY_BUCKET: KVNamespace;    # Wrong type - should be R2Bucket
  MY_DB: D1Database;        # Wrong type - should be KVNamespace
}

// wrangler.toml
[[r2_buckets]]
binding = "MY_BUCKET"       # R2 bucket, not KV!

[[kv_namespaces]]
binding = "MY_DB"           # KV namespace, not D1!

// ✅ Correct: Proper binding types
interface Env {
  MY_BUCKET: R2Bucket;      # Correct type for R2 bucket
  MY_DB: KVNamespace;       # Correct type for KV namespace
}

// wrangler.toml (same as above)
[[r2_buckets]]
binding = "MY_BUCKET"

[[kv_namespaces]]
binding = "MY_DB"

Fixing Remote Binding Configuration

// ❌ High: Missing remote binding for development
// wrangler.toml
[[kv_namespaces]]
binding = "USER_DATA"
id = "user-data"
# Missing remote = true for development!

// ✅ Correct: Remote binding configured
[[kv_namespaces]]
binding = "USER_DATA"
id = "user-data"
remote = true  # Enables remote binding for development

Fixing Secret vs Environment Variable Confusion

// ❌ High: Secret in [vars] section (visible in git)
// wrangler.toml
[vars]
API_KEY = "sk_live_12345"  # Secret exposed in git!

// ✅ Correct: Secret via wrangler secret command
// wrangler.toml (no secrets in [vars])
[vars]
PUBLIC_API_URL = "https://api.example.com"  # Non-secret config only

# Set secret via command line:
# wrangler secret put API_KEY
# (prompt: enter secret value)

// Code accesses both correctly
interface Env {
  API_KEY: string;           # From wrangler secret
  PUBLIC_API_URL: string;    # From wrangler.toml [vars]
}

MCP Server Integration

When Cloudflare MCP server is available:

• Query actual binding configuration from Cloudflare account
• Verify bindings exist and are accessible
• Check binding permissions and limits
• Get latest binding configuration best practices

Benefits

Immediate Impact

• Prevents Runtime Failures: Catches binding mismatches before deployment
• Reduces Debugging Time: Immediate feedback on configuration issues
• Ensures Type Safety: Validates TypeScript interfaces match reality

Long-term Value

• Consistent Configuration: Ensures all code uses correct binding patterns
• Better Developer Experience: Clear error messages for binding issues
• Reduced Deployment Issues: Configuration validation prevents failed deployments

Usage Examples

During Binding Usage

// Developer types: const data = await env.CACHE.get(key);
// SKILL immediately activates: "❌ CRITICAL: CACHE binding not found in wrangler.toml. Add [[kv_namespaces]] binding = 'CACHE' or check spelling."

During Interface Definition

// Developer types: interface Env { USERS: R2Bucket; }
// SKILL immediately activates: "⚠️ HIGH: USERS binding type mismatch. wrangler.toml shows USERS as KVNamespace, not R2Bucket."

During Configuration Changes

// Developer modifies wrangler.toml binding name
// SKILL immediately activates: "⚠️ HIGH: Binding name changed from USER_DATA to USERS. Update TypeScript interface and code references."

Binding Type Reference

KV Namespace

interface Env {
  MY_KV: KVNamespace;
}
// Usage: await env.MY_KV.get(key)

R2 Bucket

interface Env {
  MY_BUCKET: R2Bucket;
}
// Usage: await env.MY_BUCKET.get(key)

D1 Database

interface Env {
  MY_DB: D1Database;
}
// Usage: await env.MY_DB.prepare(query).bind(params).all()

Durable Object

interface Env {
  MY_DO: DurableObjectNamespace;
}
// Usage: env.MY_DO.get(id)

AI Binding

interface Env {
  AI: Ai;
}
// Usage: await env.AI.run(model, params)

Vectorize

interface Env {
  VECTORS: VectorizeIndex;
}
// Usage: await env.VECTORS.query(vector, options)

This SKILL ensures Workers binding configuration is correct by providing immediate, autonomous validation of binding patterns, preventing runtime failures and configuration mismatches.

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